Student Reference2

AutomotiveTechnologyCurriculum

AutomotiveTechnologyCurriculum

Module 3: Engine PerformanceSection 1: Ignition SystemsSection 1: Ignition Systems

Module 3: Engine Performance

70-1831-S

2005 EditionStudent

Reference

ENGINE PERFORMANCE: IGNITION SYSTEMS

i

Automotive Technology

Module 3: Engine Performance

Section 1: Ignition Systems

Student Reference

Produced by the Instructional Materials Laboratory1400 Rock Quarry Center

University of Missouri-ColumbiaColumbia, MO 65211

(800) 669-2465http://www.iml.missouri.edu

2005 Edition

Catalog no. 70-1831-S© 2005. The Curators of the University of Missouri.

All Rights Reserved.

TechnicalConsultant:

Robin Ferguson

ProjectCoordinator:Erica Kassel

GraphicArtists:

Chris BenedictJacqueline Craig

www.iml.missouri.edu

AUTOMOTIVE TECHNOLOGY

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ACKNOWLEDGMENTS

The 2005 revision of Engine Performance: Ignition Systems represents theInstructional Materials Laboratory’s commitment to the continual improvementof the Automotive Technology Curriculum. Engine Performance: IgnitionSystems is the first section of the third module in the nine-module series. Theother modules are as follows:

Module 1 Introduction to Automotive TechnologyModule 2 Electrical SystemsModule 3 Engine Performance, Section 2: Fuel and Exhaust SystemsModule 3 Engine Performance, Section 3: Emission Control SystemsModule 4 Engine RepairModule 5 Steering and Suspension SystemsModule 6 BrakesModule 7 Manual Drive Train and AxlesModule 8 Automatic Transmissions and TransaxlesModule 9 Heating and Air Conditioning

All modules are based on the National Automotive Technicians EducationFoundation (NATEF) task list. For years the National Institute for AutomotiveService Excellence (ASE) has set the professional standards for automotivetechnicians. A strong NATEF orientation makes the nine curriculum guides aneffective tool for preparing students to enter the technologically advanced fieldof automotive technology.

IML gratefully acknowledges the important contribution of the advisorycommittee:

Roger Donovan, Illinois Central College, East Peoria, ILRobin Ferguson, Kirksville Vocational Technical School, Kirksville, MOSam Jeanrenaud, Lee’s Summit, MOKeith Kendrick, John A. Logan College, Carterville, ILSteve Reese, Lewis and Clark Vocational Technical School, St. Charles, MORon Tuetken, Lewis and Clark Community College, Godfrey, ILJohn Walker, Hannibal Area Vocational Technical School, Hannibal, MORodney Wolken, Eldon Career Center, Eldon, MO


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TABLE OF CONTENTS

Introduction ................................................................................................................i

Title Page .............................................................................................. i

Acknowledgments ............................................................................ iii

Components ......................................................................................vii

References ........................................................................................ viii

Unit I Introduction to Ignition Systems .............................................. S 1

Lesson 1: Overview of Ignition Systems ................................... S 5

Unit II General Engine Diagnosis ....................................................... S 11

Lesson 1: Performing Preliminary Engine Diagnosis ........... S 15

Lesson 2: Performing Engine Diagnostic Tests ..................... S 23

Lesson 3: Performing Engine System Diagnostic Tests ........ S 37

Unit III Computerized Engine Controls Diagnosis and Repair .... S 55

Lesson 1: Introduction to Computerized EngineControls ......................................................................................... S 59

Lesson 2: On-Board Diagnostics and Driveability ............... S 75

Lesson 3: Test and Service Computerized EngineControl Components ................................................................... S 85

Unit IV Distributor Ignition (DI) Systems ........................................ S 113

Lesson 1: Overview and Theory of DistributorIgnition Systems ......................................................................... S 117

Lesson 2: Diagnosing and Servicing DistributorIgnition Systems ......................................................................... S 125

Unit V Electronic Ignition (EI) Systems ........................................... S 145

Lesson 1: Overview and Theory of ElectronicIgnition Systems ......................................................................... S 149


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Lesson 2: Diagnosing and Servicing ElectronicIgnition Systems ......................................................................... S 155

Unit VI Engine Related Service ........................................................... S 163

Lesson 1: Engine Related Service ........................................... S 167

Lesson 2: Oxyfuel Heating and Cutting ............................... S 183


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COMPONENTS

I. Objectives — Each unit is based on objectives that state the measurableunit and specific behavioral or performance objectives that the student isexpected to achieve. Because the objectives of the unit provide directionfor the teaching-learning process, the teacher and student need acommon understanding of the intent of the objectives.

II. Information sheets — Presented in outline format, the information sheetsprovide content essential for meeting the cognitive (knowledge) objectivesin the unit. The student should study the information sheets before anyclass discussion or completion of the assignment sheets. Thecorresponding student reference page numbers appear in the upperright- hand corner of the Instructor Guide.

III. Assignment Sheets — The assignment sheets allow the student torespond to cognitive questions in writing.

IV. Job Sheets — The job sheets are designed to guide the student throughvarious key tasks and provide a means for the instructor to evaluate astudent's performance of the task.

V. Unit Tests — The unit tests evaluate the student’s knowledge of thematerial.

VI. Priority Item Crosswalk Chart — This chart cross-references the jobsheets to the NATEF task list. A listing of the required percentages of aP-1, P-2, or P-3 item covered by the curriculum is also provided.

VII. Student Workbook and Student Test Packet Tracking Sheets — Theseprovide the instructor with an effective way to track student progress onthe assignment sheets, job sheets, and unit tests.


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REFERENCES

ALLDATA. www.alldata.com.

Automotive Excellence. Vol. 2. Peoria, IL: Glencoe/McGraw-Hill, 2001.

Dictionary of Automotive Terms. www.motorera.com/dictionary/car-dic.htm.

Dodge. www.dodge.com.

Duffy, James E. Modern Automotive Technology. Tinley Park, IL: TheGoodheart-Willcox Company, Inc., 2004.

Erjavec, Jack. Automotive Technology: A Systems Approach. 3rd ed. Albany,NY: Delmar Thomson Learning, 2000.

Ford Motor Company. www.ford.com.

General Motors. www.gm.com.

How Stuff Works. www.auto.howstuffworks.com.

Mello, Tara Baukus. “Diesel Developments.” www.edmunds.com.

National Automotive Technicians Education Foundation (NATEF).www.natef.org.

National Highway Traffic Safety Administration. Department ofTransportation. www.nhtsa.dot.gov.

National Institute for Automotive Service Excellence (ASE). www.asecert.org.

National Renewable Energy Laboratory. www.nrel.gov/vehiclesandfuels/hev/basics.html.

Tobolt, William K, Larry Johnson, and W. Scott Gauthier. AutomotiveEncyclopedia. Tinley Park, IL: The Goodheart-Willcox Company, Inc., 2000.

United States Environmental Protection Agency. www.epa.gov.

www.alldata.com

www.motorera.com/dictionary/car-dic.htm

www.dodge.com

www.ford.com

www.gm.com

www.auto.howstuffworks.com

www.edmunds.com

www.natef.org

www.nhtsa.dot.gov

www.asecert.org

www.nrel.gov/vehiclesandfuels/hev/basics.html

www.epa.gov


S 1

UNIT I: INTRODUCTION TO IGNITION SYSTEMS

CONTENTS OF THIS UNIT

I. Unit objective

II. Lesson plan

A. Lesson 1: Overview of Ignition Systems

1. Information outline

III. Unit I Test


S 2


S 3


UNIT OBJECTIVE

After completing this unit, students should be able to discuss basic ignitionsystems. Students will demonstrate mastery of the material by achieving ascore of on the Unit I Test.

SPECIFIC OBJECTIVES

After completing the lesson in this unit, students should be able to:

Lesson 1

I. Explain the purpose of ignition systems.

II. Identify the types of ignition systems.

III. Identify the basic components of ignition systems.


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S 5


LESSON 1: OVERVIEW OF IGNITION SYSTEMS

I. Purpose of ignition systems

A. Ignition systems must perform six basic functions.

1. Ignition systems turn the engine on and off.

2. Ignition systems operate using voltage from the battery oralternator.

3. Ignition systems produce high voltage at the spark plugelectrodes to being the ignition process.

4. Ignition systems fire each spark plug at the proper time.

5. Ignition systems time the spark so that it occurs on thecompression stroke when the piston nears the top of its travel,or top dead center (TDC).

6. Ignition systems control spark timing based on changes inengine load and other conditions.

B. The basic operation of the four-stroke cycle engine helps make iteasier to understand the operation of the ignition system.

1. The up-and-down movement of the piston turns thecrankshaft.

2. The crankshaft transfers its movement to the transmission/transaxle.

3. The transmission/transaxle transfers movement to the wheels.


S 6

4. To move the crankshaft, each of the pistons moves through thefour-stroke cycle, which includes the intake stroke,compression stroke, power stroke, and exhaust stroke.

a. During the intake stroke, the camshaft opens the intakevalve as the piston moves down in the cylinder. The areaof low pressure created by the downward movement ofthe piston causes the air/fuel mixture to enter thecylinder. Atmospheric pressure forces the air/fuelmixture past the intake valve and into the cylinder.

b. During the compression stroke, the rotation of thecamshaft closes the intake valve. The piston movesupward in the cylinder as the crankshaft rotates,compressing the air/fuel mixture. Near the end of thisstroke and slightly before the piston reaches TDC, thespark plug fires and ignites the air/fuel mixture.

c. During the power stroke, the air/fuel mixture explodes.The force created by the explosion causes the piston tomove downward in the cylinder and power is applied tothe crankshaft.

d. During the exhaust stroke, the piston again movesupward with the exhaust valve open. This pistonmovement forces the spent exhaust gases past the openexhaust valve. This cycle is repeated several thousandtimes a minute during normal driving.


S 7

II. Types of ignition systems

A. Distributor ignition (DI, old terms — HEI, Duraspark, TFI) systemsuse a distributor to direct current from the ignition coil to the sparkplug in each individual cylinder. The three types of DI systems arebreaker point, solid-state, and computerized.

1. Breaker point systems use breaker points, or contact points, todisrupt current to the coil primary.

NOTE: Break point systems were one of the first DI systems.

a. The breaker points, in which one is moveable and theother one is permanent, are held together by springtension. Current moves through these points to theignition coil primary.

b. The system uses a multi-lobed distributor shaft driven bythe engine crankshaft. The shaft lobes rub against themoveable point and cause it to separate from thepermanent point. This disrupts current to the ignitioncoil primary.

2. Solid-state systems use an ignition control module to disruptcurrent to the ignition coil primary.

NOTE: Solid-state systems replaced breaker point systems.

a. The main component in the ignition control module is thetransistor that switches the current to the ignition coilprimary on and off.

b. A signal from an electronic sensor activates the transistor.

3. In computerized systems, the powertrain control module(PCM) works with the ignition control module to switch thecurrent to the ignition coil on and off.

NOTE: Computerized systems replaced solid-state systems.

a. The PCM uses input from electronic sensors located oneither the crankshaft or the distributor shaft to tell theignition control module when to turn the ignition coilprimary on and off. Other sensors work with the PCM toprovide even more precise control.


S 8

B. Electronic ignition (EI, old terms — DIS, C3I, EDIS) systems do notuse a distributor to direct voltage to the individual spark plugs.Instead, they use one ignition coil for every two cylinders (wasted-spark) or one ignition coil for each cylinder (unit ignition). ThePCM advances and retards timing electronically.

NOTE: Most of today’s vehicles have EI systems. These systemsallow for efficient operation and minimal maintenance by usingelectronics to control electrical current flow.

1. A wasted-spark system uses one ignition coil for every twocylinders. Each ignition coil serves two cylinders that areopposite each other in the firing sequence. When the ignitioncoil fires, a spark is delivered simultaneously to both cylinders.

a. The ignition coil delivers the spark to one cylinder whenits piston is near the top of the compression stroke.

b. The ignition coil delivers another spark to the othercylinder when its piston is in the exhaust stroke. Thisspark does not ignite the air/fuel mixture, which is whythe system is referred to as a “wasted-spark” system.

2. A unit ignition system uses one ignition coil for each cylinder.

a. Each ignition coil fires sequentially and only on thepower stroke of the appropriate cylinder.

b. Smaller ignition coils are used because firing occurs lessfrequently than with a wasted-spark or DI system.

III. Basic components of ignition systems

A. The battery provides power to the ignition system.

B. The ignition switch is mounted on the steering column or dash andallows the driver to turn the ignition system and engine on and off.

C. The ignition coil produces the high voltage necessary to create aspark.

D. The spark plugs create a spark at their tip to ignite the air/fuelmixture in the cylinder.

E. The ignition system wires connect all the ignition components.


S 9

NOTE: DI systems use a distributor, distributor cap, and distributorrotor.

NOTE: EI systems use various electronic sensors to send signals tothe PCM.


S 10


S 11

UNIT II: GENERAL ENGINE DIAGNOSIS


I. Unit objective

II. Lesson plans

A. Lesson 1: Performing Preliminary Engine Diagnosis


2. Job sheets

a. JS1-L1-UII: Complete a Work Order with Concern,Cause, and Correction

b. JS2-L1-UII: Identify and Interpret Engine PerformanceConcern

c. JS3-L1-UII: Perform a Preliminary Engine Inspection

B. Lesson 2: Performing Engine Diagnostic Tests


2. Job sheets

a. JS1-L2-UII: Perform Engine Absolute Manifold PressureTests

b. JS2-L2-UII: Perform a Cylinder Power Balance Test

c. JS3-L2-UII: Perform Cranking Engine CylinderCompression Tests

d. JS4-L2-UII: Perform a Running Engine CylinderCompression Test

e. JS5-L2-UII: Perform a Cylinder Leakage Test

C. Lesson 3: Performing Engine System Diagnostic Tests



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2. Job sheets

a. JS1-L3-UII: Perform Engine System Diagnostic TestsUsing an Oscilloscope

b. JS2-L3-UII: Perform an Exhaust Gas Diagnostic Test

c. JS3-L3-UII: Verify Engine Operating Temperature

d. JS4-L3-UII: Inspect, Test, and Service the Cooling System

e. JS5-L3-UII: Drain, Flush, and Refill the Cooling System

f. JS6-L3-UII: Verify Correct Camshaft Timing

III. Unit II Test


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UNIT OBJECTIVE

After completing this unit, students should be able to perform general enginediagnosis. Students will demonstrate mastery of the material by successfullyperforming specific tasks on the job sheets and achieving a score of onthe Unit II Test.

SPECIFIC OBJECTIVES

After completing the lessons in this unit, students should be able to:

Lesson 1

I. Identify the functions and components of a work order.

II. Explain the procedures for verifying a customer’s engine performanceconcern.

III. Explain the procedures for performing a preliminary engine inspection.

IV. Demonstrate the ability to:

A. Complete a work order with concern, cause, and correction(JS1-L1-UII).

B. Identify and interpret engine performance concern (JS2-L1-UII).

C. Perform a preliminary engine inspection (JS3-L1-UII).

Lesson 2

I. Explain the procedures for performing engine absolute (vacuum/boost)manifold pressure tests.

II. Explain the procedures for performing a cylinder power balance test.

III. Explain the procedures for performing engine cylinder compression tests.

IV. Explain the procedures for performing a cylinder leakage test.

V. Demonstrate the ability to:

A. Perform engine absolute manifold pressure tests (JS1-L2-UII).


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B. Perform a cylinder power balance test (JS2-L2-UII).

C. Perform cranking engine cylinder compression tests (JS3-L2-UII).

D. Perform a running engine cylinder compression test (JS4-L2-UII).

E. Perform a cylinder leakage test (JS5-L2-UII).

Lesson 3

I. Explain the procedures for performing engine system diagnostic testsusing an oscilloscope.

II. Explain the procedures for performing an exhaust gas diagnostic test.

III. Explain the procedures for verifying engine operating temperature.

IV. Explain the procedures for inspecting, testing, and servicing the coolingsystem.

V. Explain the procedures for verifying correct camshaft timing.

VI. Demonstrate the ability to:

A. Perform engine system diagnostic tests using an oscilloscope(JS1-L3-UII).

B. Perform an exhaust gas diagnostic test (JS2-L3-UII).

C. Verify engine operating temperature (JS3-L3-UII).

D. Inspect, test, and service the cooling system (JS4-L3-UII).

E. Drain, flush, and refill the cooling system (JS5-L3-UII).

F. Verify correct camshaft timing (JS6-L3-UII).


S 15


LESSON 1: PERFORMING PRELIMINARY ENGINE DIAGNOSIS

I. The automotive technician needs to be familiar with the functions andcomponents of a work order.

NOTE: See JS1-L1-UII for a sample work order.

A. The work order serves several functions.

1. Itemizes the repairs by listing the cost of parts and labor

2. Can be used to authorize the repair

3. Has the necessary information on how to contact the ownerand serves as documentation for future reference

4. May also specify limited warranties and liabilities of the shop

5. May serve as a reference for recent service history for warrantyor legal purposes

B. A work order typically has the following components.

1. Customer name, address, and phone number (home or workwith extension number)

2. Date

3. Invoice number

4. Year, make, model, vehicle identification number (VIN), andmileage of the vehicle

5. Name/initials of the service writer and technician

6. Customer authorization signature to allow repairs

7. Description of customer concern

8. Vehicle service history information

9. Related technical service bulletins (TSB)


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10. Technician's notes that includes diagnostic proceduresperformed, the results of diagnosis, and any importantobservations or remarks

11. Component or system defect responsible for the concern

12. Service performed to successfully correct the concern

13. Labor procedures and costs based on the parts and laborestimation guides

14. Outside labor procedures and costs that include if a shop senta particular part out to another shop for repairs

15. Listing of each part that includes name, description, and cost

16. Sales tax, which is usually calculated on parts only

17. Total that represents the final price that the customer will payfor all charges related to the repair

C. Work orders may be handwritten or prepared by entering codes in acomputer terminal and then printed.

D. Depending on the part, the following information may be requiredfor ordering repair parts.

1. Make, model, and model year (found on the driver’s side doorjamb) of the vehicle

2. VIN

3. Engine information that includes engine size, in cubic inchesor liters, the number of cylinders, and the type of fuel system

4. Wheelbase

5. Number of doors

II. Procedures for verifying a customer’s engine performance concern

A. It is very important to verify the customer’s concern beforebeginning engine performance diagnosis.

B. Have the customer describe the engine performance concern. Paycareful attention to what he or she is describing. Make sure torecord what is said.


S 17

C. Ask the customer the following series of questions. Make sure torecord answers.

1. When did the concern first occur?

2. Is the malfunction indicator light on or flashing?

3. Is the concern continuous or intermittent?

4. What are the driving conditions when the concern occurs?

5. Is the vehicle making any unusual noises or vibrations?

6. What is the recent service history of the vehicle?

D. Based on the answers to the questions, determine the next step inthe diagnostic process for the vehicle.

III. Procedures for performing a preliminary engine inspection

A. Many engine performance problems can be traced to somethingsimple. A preliminary engine inspection is an important part ofdiagnosing engine problems and saves diagnostic time.

B. Perform a preliminary engine inspection.

1. With the engine off, inspect the installation and routing of thespark plug wires.

a. Check each wire to make sure it is securely installed onthe spark plugs and distributor cap.

b. Check the routing of the wires for contact with hotexhaust parts or moving parts.

2. Inspect the condition of the primary wiring terminals andconnectors for secure connections. Check for improperlyrouted or damaged wiring.

3. Inspect the battery terminals for corrosion or looseness.

4. Inspect the air filter for cleanliness of the elements. A dirty airfilter produces an overly rich air/fuel mixture that results inpoor fuel economy, poor performance, and higher-than-normal exhaust emissions.


S 18

5. Inspect the drive belts for looseness or wear. Damaged drivebelts can slip and cause an engine to overheat. This can alsocause low alternator output that results in a no-start conditionor poor performance due to low system voltage.

6. Inspect for oil leaks on the spark plug wires and other parts.These are messy and can be a potential fire hazard.

7. Check the coolant level. Low coolant level can causeoverheating and loss of performance.

NOTE: The coolant level is critical in engines controlled bycomputers. A slightly low coolant level may not cause engineoverheating but can keep the engine coolant temperaturesensor from functioning properly.

8. Inspect for coolant leaks. These can cause a misfire problem,can result in a low coolant level, and can cause engineoverheating.

9. Inspect for fuel leaks. These are a fire hazard and must becorrected. Inspect the fuel tank, fuel lines, fuel pump, andcarburetor/fuel injectors for leaks.

10. Inspect for any other leaks that may cause a problem.

C. Diagnose abnormal engine noises or vibrations.

1. Abnormal engine noises or vibrations indicate engine wear ordamage.

2. Different methods can be used to locate abnormal enginenoises or vibrations.

CAUTION: Use these methods outdoors because thevehicle must be started without exhaust ventilationequipment connected to the tailpipe.

a. A stethoscope is a listening device used to find internalnoises in parts. Place the stethoscope against the suspectpart. The stethoscope magnifies the sound to make itclear and loud.

b. A long screwdriver can be used in place of a stethoscope.Noises travel through the screwdriver similar to astethoscope.


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c. A section of vacuum hose can be used to locate vacuumleaks and air pressure leaks. Place one end of the hosenext to the ear and move the other end around theengine compartment. The hiss is loudest when the hoseis near the suspect part.

3. The following are possible sources of abnormal engine noisesor vibrations.

a. Rod bearing knock is a light, regular, rapping noise thatoccurs when the throttle is held constant and the engineis not accelerating. It is loudest after engine warm-up.

b. Main bearing knock is similar to rod bearing knock but isslightly deeper or duller in pitch and is normally louderwhen the engine is under load.

c. A worn main thrust bearing causes excess crankshaftendplay. On vehicles equipped with manualtransmissions, a deep knock when applying and releasingthe clutch is produced. On vehicles equipped withautomatic transmissions, a single thud or knock duringacceleration or deceleration is produced.

d. Piston slap is a loud, metallic knock produced when thepiston flops back and forth inside its cylinder. Piston slapis normally louder when the engine is cold and quieter asthe engine reaches normal operating temperature.

e. Piston pin knock is caused by excessive clearancebetween the piston pin and the pin bore in the piston.

f. Vacuum leaks produce a high-pitched, hissing orsquealing noise and are often misdiagnosed as a defectivealternator, water pump, or idler pulley bearings.Vacuum leaks often change when the throttle is openedquickly or when the engine is under load.

g. A cracked flywheel/flex plate is often misdiagnosed asrod bearing knock or main bearing knock.

h. Exhaust leaks produce a clicking sound especially duringacceleration and can be misdiagnosed as a noisy valve.

i. Valve train noise is caused by a lack of oil to the liftersand is most noticeable at idle when oil pressure is lowest.


S 20

j. An excessively loose timing chain produces a severeknocking noise when the timing chain hits the timingchain cover. This can be misdiagnosed as rod bearingknock.

k. A overly tight timing belt produces a whining sound.Damage to timing belt covers produces a rubbing orgrinding sound.

l. When the attaching nuts or bolts on a torque converterare loose on the flex plate, the noise is most noticeable atidle or when the engine is not under load.

m. Loose or defective drive belts produce a flopping noisethat sounds similar to bearing knock.

n. An early fuel evaporative valve produces a knockingnoise especially under load.

o. Defective engine mounts produce a clunking soundusually during acceleration.

p. Pre-ignition produces a pinging sound caused by ignitionof the air/fuel mixture before the timed spark ignition.

q. Detonation produces a loud, audible knock caused by aviolent explosion in the combustion chamber created bythe uncontrolled burning of the air/fuel mixture.

r. Secondary ignition produces a snapping or clickingsound caused by the jumping of high voltage current.

s. Vehicle accessories, such as the power steering pump, airpump, or air conditioning compressor, produce floppingnoises, grinding noises, whining noises, rattling noises, orclattering noises.

D. Inspect for abnormal exhaust color, odor, and sound.

NOTE: Analyzing exhaust fumes does not provide a conclusivediagnosis of the problem. It does provide direction for furtherdiagnosis.

CAUTION: The following test should be performed outdoorsbecause it must be done without exhaust ventilation equipmentconnected to the tailpipe.


S 21

1. Start the engine.

2. When the engine first starts, look for any signs of heavy blacksmoke and/or an uneven sound coming from the exhaust.This indicates that the choke or cold enrichment system is toorich.

NOTE: Light traces of black or white smoke emitted uponstart-up is normal. The white smoke is created by water vaporin the exhaust and should dissipate as the engine begins toreach normal operating temperature.

3. While the engine is at a warm idle, listen to the exhaustsystem. The system should sound reasonably even and steady.An uneven sound, fluttering, or popping in the exhaust mayindicate a carburetor problem, ignition miss, or an internalengine problem such as a leaking valve.

4. Raise the engine speed to 2,000 rpm and listen to theexhaust. If the exhaust sound is not smooth, the problem maybe with the ignition system or internal workings of the engine.

5. Note the exhaust color.

a. With the engine at normal operating temperature, theexhaust should be colorless.

NOTE: On extremely cold days, it is normal for theexhaust to have a white vapor.

b. Engine coolant leaking into the combustion chamberusually causes white smoke in the exhaust. A defectivecylinder head gasket, cracked cylinder head, or engineblock are the most likely causes.

c. Blue smoke is normally a sign of oil in the combustionchamber. Oil can enter the combustion chamber throughworn or broken piston rings, defective valve stem seals,defective intake manifold gaskets, plugged oil returnholes in the cylinder head, or a leaking automatictransmission vacuum modulator diaphragm.

6. Check for any unusual exhaust odor.

a. White smoke from the engine coolant that leaks into thecombustion chamber produces an unpleasantly sweetsmell.


S 22

b. An overly rich air/fuel mixture on vehicles equippedwith a catalytic converter produces a rotten egg or sootysmell.

c. Blue smoke produces a burning oil smell.

E. Based on the preliminary engine inspection, determine the next stepin the repair process. Further diagnosis and/or repairs should beincluded in the steps.


S 23


LESSON 2: PERFORMING ENGINE DIAGNOSTIC TESTS

NOTE: Testing the engine’s mechanical condition is required when the causeof a problem is not located during the preliminary inspection. Enginediagnostic tests are designed to locate internal engine problems.

I. Procedures for performing engine absolute (vacuum/boost) manifoldpressure tests

A. Perform a vacuum gauge test to determine engine condition andperformance.

NOTE: Accurately diagnosing problems with a vacuum gauge canbe difficult. Study and compare readings to diagnostic charts.

1. Connect the vacuum gauge to an intake manifold vacuumsource. Connect a vacuum hose to an accessible intakemanifold vacuum connector and extend it up to the vacuumgauge.

2. Connect the exhaust ventilation equipment.

CAUTION: Be sure to use approved exhaust ventilationequipment when operating a vehicle in an enclosed area.

3. Start the engine and allow it to reach normal operatingtemperature.

4. Observe and record the reading with the engine at idle speed.Normal idle vacuum is approximately between 18 in and 21 in.A low reading or an erratic vacuum gauge needle indicates aproblem.


S 24

5. Shut off the engine. Disconnect the test equipment.Disconnect the exhaust ventilation equipment.

B. Perform an exhaust restriction test to determine if the exhaustsystem is restricted or has excessive back pressure.

1. Connect the vacuum gauge to an intake manifold vacuumsource. Connect a vacuum hose to an accessible intakemanifold vacuum connector and extend it up to the vacuumgauge.

2. Connect a tachometer to the engine.



4. Start the engine. Gradually accelerate the engine rpm fromidle to 2,000 rpm. Observe and record the reading.

5. Maintain the engine speed at 2,000 rpm for about 10 secondsor longer. Observe and record the reading. The vacuumgauge should hold steady or increase slightly. The vacuumreading gradually decreases if the exhaust system is restricted.


C. Perform a cranking vacuum test to determine if the engine ismechanically sound.



2. Start the engine and allow it to reach normal operatingtemperature. Shut off the engine.

3. Connect a vacuum gauge to a nonported vacuum source onthe intake manifold.

4. Disable the ignition system.

5. Completely block the throttle valve so that air cannot enter.


S 25

6. Crank the engine. Observe and record the cranking vacuum.

7. Disconnect the vacuum gauge.

8. Unblock the throttle valve. Enable the ignition. Disconnect theexhaust ventilation equipment.

9. The following are possible results for this test.

a. Satisfactory cranking vacuum indicates a mechanicallysound engine.

b. Uneven or pulsating cranking vacuum indicates defectivevalves, defective piston rings, a defective head gasket, oran uneven cranking speed.

c. Below normal cranking vacuum indicates excessiveresistance in the battery cables, a defective crankingmotor, or excessive mechanical drag in the engine.

d. Uneven cranking vacuum indicates uneven compressionor a defective starter.

NOTE: If the cranking vacuum is uneven, perform acranking engine cylinder compression test or a cylinderleakage test. Satisfactory engine performance cannot beobtained until existing compression or vacuum leaks areeliminated.

D. Based on the tests, determine the necessary action to correct anyproblems. Include further diagnosis and/or repairs.

II. Procedures for performing a cylinder power balance test

A. Perform a cylinder power balance test to determine if a cylinder issupporting its share of engine load. The purpose of the test is tocompare the difference in the percentage of rpm drop. The variancebetween cylinders should not exceed 20%.

1. Connect the cylinder balance tester to the engine according tomanufacturer’s procedures.

NOTE: This test may also be performed using an engineanalyzer or scan tool.

2. Connect a tachometer to the engine if it is not part of thecylinder balance tester.


S 26

NOTE: The tachometer is necessary because the drop inengine rpm is viewed on the tachometer.



4. Start the engine and allow it to reach normal operatingtemperature. Shut off the engine.

5. Disconnect the oxygen sensor and unplug the exhaust gasrecirculation (EGR) hose or connector.

6. Restart the engine. Bring the engine speed to 1,000 rpm andmaintain that speed.

7. Select the cylinder shorting mode on the cylinder balancetester. Disable the idle air control on a fuel-injected engine,which is necessary because it compensates for the shortedcylinder and raises the engine rpm.

8. Short each cylinder for the same amount of time, about 2seconds to 3 seconds. Give the engine about 5 seconds tostabilize between each short.

NOTE: All shorted cylinders should cause the rpm to drop acertain percentage.

9. Observe the tachometer for the amount of rpm drop on eachcylinder. Compare the reading to the following specifications.

a. A four-cylinder engine should have a 10% to 18% drop inrpm.

b. A six-cylinder engine should have an 8% to 12% drop inrpm.

c. An eight-cylinder engine should have a 4% to 8% drop inrpm.

NOTE: All cylinders should drop about the sameamount.

NOTE: Check a cylinder that does not show rpm dropbecause this causes a cylinder to miss.


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11. Reconnect the oxygen sensor and the EGR hose or connector.

12. Clear the codes.

13. Based on the tests, determine the necessary action to correctany problems. Include further diagnosis and/or repairs.

III. Procedures for performing engine cylinder compression tests

A. There are two types of engine cylinder compression tests.

1. A cranking engine cylinder compression test accuratelyidentifies leaking piston rings, leaking valves, or a blown headgasket.

2. A running engine cylinder compression test determinesvolumetric efficiency.

B. Volumetric efficiency is the measure of the quantity of air broughtinto the cylinder during various engine operating conditions. It isproportional to the airflow that is limited by the quantity that canflow past the valves and into the combustion chamber.

1. After a certain rpm, the amount of pressure in the combustionchamber starts to decrease. The amount of restriction causesreduced airflow and low compression.

2. Volumetric efficiency is illustrated by cranking, idle, and snapacceleration compression.

a. Cranking compression

1. The throttle is closed during cranking. The totalairflow into the combustion chamber is limited bythe quantity of air that can flow past the throttleplate and through the idle air bypass.

2. The quantity of air entering the combustionchamber is 80% of the total capacity at wide openthrottle. About 150 pounds per square inch (psi) ofcompression at wide open throttle can be expected.


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3. If the throttle plate is closed during cranking, adecrease in pressure should occur.

4. If compression does not increase when the throttleopens during a cranking engine cylindercompression test, there is a restriction in the intakeor exhaust airflow.

b. Idle compression

1. When the engine idles, the throttle position closes,but the rpm is approximately three times faster thanthe cranking rpm.

2. Because the total volume of the air/fuel mixturebeing drawn into the cylinder is less due to thethrottle position and engine rpm, the idlecompression is reduced to about 100 psi. The pistonmoves faster than the air because of the restrictioncaused by the closed throttle plate.

3. Characteristics of idle compression

• The air is restricted by the throttle plate.

• The crankshaft speed is four to five timesfaster than the cranking speed.

• There is less air entering the cylinder perengine cycle.

• There is typically 50 psi to 60 psi, and thegauge must be “burped.”

• If the rpm increases slowly, the pressuredecreases.

• There are no manufacturer’s specifications tocompare with other cylinders.

c. Snap acceleration compression

1. By snap accelerating the throttle, the compressionincreases and the area for air movement increasesabout 80 times.


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2. The throttle opening allows more of the air/fuelmixture into the cylinder in the same short time.

3. The increased compression with more fuel producesincreased power and causes the rpm to increase,resulting in higher running compression pressureand more power.

4. When the throttle quickly snaps open to remove thethrottle plate restriction, the readings increase toabout 80% of cranking compression.

• A high reading indicates an exhaust restrictionthat is most likely caused by an exhaust valvetrain problem.

• A low reading indicates an intake restrictionmost likely caused by an intake valve trainproblem or a carboned valve.

C. There are differences between a cranking engine cylindercompression test and a running engine cylinder compression test.

1. A cranking engine cylinder compression test isolates a cylinderseal problem, and a running engine cylinder compression testshows a volumetric efficiency problem.

2. By snapping the throttle, the airflow into the enginedramatically increases and an increase in the compressionpressure occurs.

3. It is possible to compare the series of readings with the othercylinders to isolate the best candidate for a potentialvolumetric efficiency problem.

D. There are variables that affect a running engine cylindercompression test.

1. The compression relationship on a running engine is about 60psi at idle and about 40 psi when accelerating to 1,500 rpm.The throttle position and engine rpm restrict the amount of airthat can enter the cylinder when compared to idle rpm.

2. With the engine running, the piston moves faster than theairflow into the cylinder through the small passage created bythe closed throttle plate.


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3. Similar to a slow-crank condition, the cylinder is not as full ofair as it can be. This results in the running compression beingless than cranking compression.

4. Because the piston moves much faster in running compression,the normal cylinder seal leakage and heat loss to the cylinderwalls are reduced to almost nothing. The result is highercompression temperature and a spark that easily ignites theair/fuel mixture.

E. Perform cranking engine cylinder compression tests.

1. Perform a cranking engine cylinder compression test with thethrottle closed.

a. Connect the exhaust ventilation equipment.

CAUTION: Be sure to use approved exhaustventilation equipment when operating a vehicle in anenclosed area.

b. Start the engine and allow it to reach normal operatingtemperature.

c. Shut off the engine.

d. Disable the ignition and fuel systems.

e. Remove the air filter.

f. Use compressed air to blow debris away from the sparkplugs. Remove the spark plugs.

g. Install the compression gauge in one cylinder.


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h. Crank the engine at least four compression strokes. If theengine cranks slowly, the readings are not accurate.Charge the battery. Then, test the battery, starting, andcharging systems. It may be necessary to keep a batterycharger on the battery to perform this test.

i. Observe the compression gauge. Record the readings ofthe first “puff” and at the highest point.

j. Repeat the procedure for each cylinder.

k. Remove the compression gauge. Reinstall the air filterand spark plugs. Enable the ignition and fuel systems.Disconnect the exhaust ventilation equipment.

2. Perform a cranking engine cylinder compression test with thethrottle open.



b. Start the engine and allow it to reach normal operatingtemperature.

c. Shut off the engine.

d. Disable the ignition and fuel systems.

e. Remove the air filter.

f. Block the throttle valve to the wide open position.

g. Use compressed air to blow debris away from the sparkplugs. Remove the spark plugs.

h. Install the compression gauge in one cylinder.

i. Crank the engine at least four compression strokes. If theengine cranks slowly, the readings are not accurate.Charge the battery. Then, test the battery, starting, andcharging systems. It may be necessary to keep a batterycharger on the battery to perform this test.


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j. Observe the compression gauge. Record the readings ofthe first “puff” and at the highest point.

k. Repeat the procedure for each cylinder.

l. Unblock the throttle valve.

m. Remove the compression gauge. Reinstall the air filterand spark plugs. Enable the ignition and fuel systems.Disconnect the exhaust ventilation equipment.


a. If the first “puff” is low but gradually builds up to anormal reading, there could be a worn ring or cylinderwall problem.

b. If the reading is higher than specifications or higher onone cylinder, there could be carbon buildup or acamshaft problem.

c. If the reading remains the same on some strokes or isslow on others or if different readings occur onsubsequent tests of the same cylinder, there could be asticking valve.

F. Perform a running engine cylinder compression test.




3. Shut off the engine.

4. Use compressed air to blow debris away from the spark plugs.Remove one spark plug and connect a spark tester to the plugwire.

5. Install the compression gauge in the cylinder.

6. Start the engine and allow it to idle.


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7. Release the compression gauge pressure.

8. Observe and record the compression reading at idle.

9. Slowly raise the engine speed to 1,500 rpm. Observe andrecord the compression reading.

10. Return the engine speed to idle.

11. Release the compression gauge pressure.

12. Snap the throttle open and then closed. Observe and recordthe compression reading.

NOTE: Attempt to open the throttle as wide as possiblewithout increasing the engine speed because this allows moreair in without increasing the rpm.

13. Repeat the procedure for each cylinder. Compare the readingsto the following specifications.

a. Compression at idle should be 100 psi (+/-20).

b. Compression at 1,500 rpm should be 60 psi (+/-20).

c. Compression when snapping the throttle open andclosed should be 80% of wide open throttle crankingcompression.


15. Remove the compression gauge. Remove the spark tester andreinstall the spark plug.

16. Disconnect the exhaust ventilation equipment.


IV. Procedures for performing a cylinder leakage test

A. Perform a cylinder leakage test to determine the amount ofcompression loss in a cylinder and pinpoint the source ofcompression leakage.



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CAUTION: Be use to use approved exhaust ventilationequipment when operating a vehicle in an enclosed area.



4. Remove the air filter.

5. Block the throttle valve to the wide open position.

6. Use compressed air to blow debris away from the spark plugs.Remove the spark plugs.

7. Remove the crankcase filler cap.

8. Check the coolant level. If necessary, refill the radiator.

9. Rotate the engine until the cylinder is at top dead center(TDC).

10. Calibrate and connect the cylinder leakage tester according tomanufacturer's procedures.

11. Observe and record the reading.

12. Repeat the procedure for each cylinder. Compare thereadings to the following specifications.

a. If engine condition is excellent, leakage is 0% to 4%.

b. If engine condition is good, leakage is 5% to 9%.

c. If engine condition is fair, leakage is 10% to 14%.

d. If engine condition is poor, leakage is 15% to 20%.


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13. If there is excessive cylinder leakage, listen at the differentpoints to determine the source of the leak.

Location to Listen or Look for Air Leak Problem Component Exhaust tailpipe Exhaust valve Throttle valve Intake valve Oil filler cap or positive crankcase ventilation valve connection

Piston rings

Spark plug hole of each cylinder Head gasket Air bubbles in the radiator Cylinder head or block (may be cracked)

Head gasket (leaking into cooling system)

14. Disconnect the cylinder leakage tester.

15. Unblock the throttle valve.

16. Reinstall the air filter and spark plugs. Replace the crankcasefiller cap.

17. Disconnect the exhaust ventilation equipment.



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LESSON 3: PERFORMING ENGINE SYSTEM DIAGNOSTIC TESTS

I. Procedures for performing engine system diagnostic tests using anoscilloscope

A. An oscilloscope, or scope, displays voltage in relation to time. Itproduces a line on a cathode ray tube (CRT) or liquid crystal display(LCD) when connected to circuit voltage. A circuit problem can befound by comparing the line “pattern” to a known good pattern.

1. The display pattern, or trace, is the circuit voltage pattern.

2. The vertical pattern represents voltage. The higher the verticalrise is, the higher the voltage is from the device being tested.

a. Oscilloscopes have a selector for voltage scales. There areprimary/secondary and high/low selector switches thatresult in four voltage scales.

1. The primary low voltage scale has a 0 to 25 voltrange.

2. The primary high voltage scale has a 0 to 250 voltrange.


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3. The secondary low voltage scale has a 0 to 25kilovolt range.

4. The secondary high voltage scale has a 0 to 50kilovolt range.

3. The horizontal pattern represents time. Time is represented onthe screen in degrees, milliseconds, or duty cycle. Dwell canactually be seen and measured on an oscilloscope.

4. An oscilloscope requires input from at least four locations: theprimary circuit, the secondary circuit, reference signal to locatesequence (usually the number 1 spark plug wire), and ground.

B. Check for continuity when observing oscilloscope patterns. Eachcylinder should be basically the same as the others.

1. A parade pattern is horizontal on the screen with the cylinderpatterns side-by-side in firing order, starting with the number 1cylinder on the left. A parade pattern allows all sections of thepattern for each cylinder to be viewed at the same time.


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2. A raster pattern has all cylinders on the screen one above thenext. The firing order starts with the number 1 cylinder at thebottom of the stack and the last cylinder at the top of the stack.The advantage of the raster pattern is it measures timevariations from cylinder to cylinder.

3. The superimposed pattern stacks all patterns on top of eachother to look like a single cylinder with only small variations.This pattern is used to compare spark line variations, but itcannot indicate which cylinders are at fault.


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4. In distributor ignition (DI) systems, the primary and secondarypatterns show the same events, but more can usually bedetermined from viewing the secondary pattern. Thesecondary pattern is divided into three sections: the firingsection, intermediate section, and dwell section.

a. The firing section is the first section displayed on the leftside of the screen. This section displays the buildup ofvoltage in each cylinder circuit.

1. The long vertical line is called the firing spike.

2. Current flow across the spark plug electrodes andto ground is displayed.

3. The horizontal trace from A to B is called the sparkline, or firing line.

b. The intermediate section begins when the spark plugstops firing and the remaining voltage from the coilsecondary dissipates. This is referred to as coiloscillations.

c. The dwell section is displayed last and begins with theignition module switching on to provide current to theprimary circuit. This section ends with the ignitionmodule switching off the primary current to fire theignition coil.


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5. In electronic ignition (EI) systems, secondary oscilloscopepatterns share many of the characteristics of computerized DIsystem patterns, but there are some unique characteristics.

a. In a wasted-spark ignition system, two firing spikes aredisplayed.

1. A true firing shows the voltage required to cross thespark plug gap on the cylinder in its power stroke.

2. A wasted firing shows the voltage required to crossthe spark plug gap on the cylinder in its exhauststroke.

C. Perform engine system diagnostic tests using an oscilloscope.

1. Connect the oscilloscope to the engine according tomanufacturer’s procedures.

2. Check service information and record the engine size, dwelltime, and firing order.


CAUTION: Be sure to use approved exhaust ventilationequipment when operating the vehicle in an enclosed area.


5. Check the primary raster pattern for dwell time, primary on,primary off, coil oscillations, and uneven primary off trace.Compare patterns to manufacturer’s specifications.

6. Check the secondary parade pattern for even firing spikes,normal firing lines, and similarity between cylinders. Comparepatterns to manufacturer’s specifications.

NOTE: The firing spikes should be within 3 kilovolts of eachother and between 5 kilovolts and 15 kilovolts in height.


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7. Check the secondary raster pattern for even firing lines,primary on, dwell time, and coil oscillations. Comparepatterns to manufacturer’s specifications.

8. Shut off the engine and disconnect the oscilloscope.Disconnect the exhaust ventilation equipment.

9. Based on the tests, determine necessary action to correct anyproblems. Include further diagnosis and/or repairs.

II. Procedures for performing an exhaust gas diagnostic test

A. The exhaust gas analyzer measures chemical content of exhaustgases and indicates the amount of pollutants and other gases in theexhaust. This determines condition of the engine and other systems.

1. Depending on the type of exhaust gas analyzer, the techniciancan measure hydrocarbons (HC), carbon monoxide (CO),carbon dioxide (CO2), oxygen (O2), and oxides of nitrogen(NOx).

2. Exhaust gas analysis indicates excessive emissions resultingfrom problems, such as a clogged air filter, engine mechanicalproblems, a vacuum leak, an ignition system malfunction, anemissions control system malfunction, a fuel metering problem,and/or a computer system malfunction.

B. The three types of exhaust gas analyzers are the two-gas, four-gas,and five-gas.

1. The two-gas analyzer measures the amount of HC and CO.This analyzer is rarely used because it cannot analyze theexhaust gases on modern engines.

2. The four-gas analyzer measures the amount of HC, CO, CO2,and O2.

3. The five-gas analyzer measures HC, CO, CO2, O2, and NOx.This analyzer provides the most information about exhaustgases.

C. Exhaust gas analyzer readings must be within specifications set byeach state. Modern vehicles have stricter specifications and requirelower readings than older vehicles.


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1. HC are measured in parts per million (ppm) by volume. Areading of 20 ppm means there are 20 parts of HC for everymillion parts of exhaust gas.

a. Excessive HC in the exhaust causes a rotten egg smell.This can be caused by a fuel system malfunction,incorrect ignition timing, engine mechanical problems, anemissions control system malfunction, an ignition systemmalfunction, and/or a computer system malfunction.

2. CO is measured in percentage by volume. A reading of 1.2%means that 1.2% of the engine exhaust is CO.

a. A high CO reading indicates an overly rich air/fuelmixture because of incomplete burning of fuel or a lack ofO2 during combustion. This can be caused by a fuelsystem malfunction, an emissions control systemmalfunction, and/or incorrect ignition timing.

b. A low or no CO reading indicates a lean air/fuelmixture.

3. CO2 is measured in percentage by volume. The CO2 readingshould typically be above 8%.

a. CO2 is a by-product of combustion and is not toxic at lowlevels.

b. Compare the CO2 and O2 readings when evaluating theexhaust gases. These readings indicate the air/fuelmixture ratio and possible exhaust leaks.

4. O2 is measured in percentage by volume. The O2 readingtypically should be between 1% and 7%.

a. O2 is needed in the exhaust gases for the catalyticconverter to burn the HC and CO emissions. O2 is addedto the exhaust gases by the air injection system or theexhaust pulse air injection system.

5. NOx are measured in ppm by volume and can be measuredonly with a five-gas analyzer. High NOx can be caused byhigh combustion chamber temperatures and/or an exhaustgas recirculation system malfunction.

NOTE: Because NOx are toxic, many states have madeexhaust testing with a five-gas analyzer mandatory.


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D. Perform an exhaust gas diagnostic test.

1. Connect the exhaust gas analyzer according to manufacturer’sprocedures.

NOTE: It may be necessary to block the source of air to thecatalytic converter. A catalytic converter that works properlycleans the exhaust gases and makes it difficult to get anaccurate reading.

2. Turn on the exhaust gas analyzer and allow it to warm up.

3. Zero and calibrate the exhaust gas analyzer.


5. Check the exhaust gas analyzer readings. Compare readingsto proper specifications.

6. Shut off the engine. Disconnect the exhaust gas analyzer.

7. Based on the test, determine necessary action to correct anyproblems. Include further diagnosis and/or repairs.

III. Procedures for verifying engine operating temperature

A. Engine operating temperature is the temperature the engine coolantreaches under normal operating conditions. Engine operatingtemperature is typically between 180°F and 210°F (80°C and100°C).

B. The safest and easiest method to verify engine operatingtemperature is to use a noncontact infrared thermometer.



2. Start the engine and allow it to run until warm.

3. Aim the infrared thermometer at the cylinder head andmeasure the temperature. Compare reading to manufacturer’sspecifications.


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4. Shut off the engine. Disconnect the exhaust ventilationequipment.


C. Verify engine operating temperature using a digital multimeter(DMM) with a temperature probe.

1. Place the temperature probe on the engine near thethermostat, on the top radiator hose, or into the coolant in theradiator (not in the overflow recovery tank).

CAUTION: Be sure the temperature probe is designed tobe placed in a liquid.

CAUTION: Never remove a radiator cap unless the engineis sufficiently cool. Removing the radiator cap when theengine is hot can cause scalding hot coolant to be sprayedover a wide area, resulting in serious injury.




4. Monitor the temperature reading. Compare reading tomanufacturer’s specifications.



D. Verify engine operating temperature using a direct-read, probe-type(cooking) thermometer.

1. Place the thermometer probe into the coolant in the radiator ortape the thermometer to the top radiator hose.




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4. Observe the reading. Compare reading to manufacturer’sspecifications.



IV. Procedures for inspecting, testing, and servicing the cooling system

A. Inspect the cooling system.

1. Inspect the radiator cap for damage. Check the rubber ormetal seal for cracks.

2. Inspect the hoses for wear, holes, swollen areas, and flexibility.

3. Inspect the outer shell of the radiator for cracks and holes.

4. Inspect the coolant passages inside the radiator. If the coolantpassages are restricted, the radiator must be sent to a specialtyshop to be rodded out.

5. Inspect the coolant recovery tank for cracks or holes.

B. Pressure test the cooling system for leaks.

1. Connect a pressure tester to the radiator filler neck.

CAUTION: Never remove a radiator cap unless the engineis sufficiently cool. Removing the radiator cap when theengine is hot can cause scalding hot coolant to be sprayedover a wide area, resulting in serious injury.


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2. Pump the pressure tester until the pressure reaches the releasepressure marked on the radiator cap. Check the coolingsystem for leaks.

a. Check for signs of leaks at the radiator tank and coolingfins and tubes.

b. Check for leaks from the heater core on the ground orfloor under the engine and on the right front carpet in thepassenger compartment.

c. Check for leaks at the water pump drive shaft where thepulley is connected. Replace the water pump if leakage isfound.

d. Check all hoses and hose connections for leaks.

e. Check engine and thermostat gaskets for leaks.

f. Check engine freeze (core) plugs for leaks.

g. Check engine oil and transmission fluid for coolantcontamination.

3. Monitor the reading for 15 minutes. Pressure should not dropmore than 1 or 2 lb in a 15-minute period. A drop in pressureindicates cooling system leakage.

4. Relieve the pressure and disconnect the pressure tester.

5. Connect the pressure tester to the radiator cap and test thepressure release point. Replace the radiator cap if the test doesnot meet manufacturer’s specifications.

6. Relieve the pressure and disconnect the pressure tester.

C. Test the cooling system for combustion gas leakage.

1. Test using a pressure tester.




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b. Connect the pressure tester. Do not pressurize thecooling system.

c. Start the engine and monitor the reading. A rapidincrease in pressure indicates cylinder compressionleakage into the cooling system.

d. Shut off the engine. Disconnect the pressure tester andthe exhaust ventilation equipment.

2. Test using a combustion leak tester.



b. Place the tester in the filler opening of the cooling system(radiator or reservoir).

c. Start the engine. Squeeze and release the tester bulb toget an air sample.

d. Observe the color of the test fluid in the tester. Blueindicates no combustion gases and yellow indicatescombustion gases are leaking into the cooling system.

e. Shut off the engine. Disconnect the exhaust ventilationequipment.

3. Test using an exhaust gas analyzer.



b. Remove the filler cap (radiator or reservoir).

c. Start the engine. Place the exhaust gas analyzer probenear the cooling system filler opening.

d. Observe the readings and increase engine speed. A HCreading indicates combustion gas is leaking into thecooling system.


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CAUTION: Do not allow coolant to be sucked into theexhaust gas analyzer. Coolant pulled into the analyzerwill damage the analyzer.


D. Inspect the condition of the coolant.

1. Remove the radiator cap.

2. Check the coolant color. It should have a good color and stillbe clear and not clouded by contamination.

3. Feel the coolant between the fingers. It should feel slippery.

4. If the coolant looks cloudy, is a dark or rusty color, is foamy, orfeels gritty or sticky, it should be replaced immediately.

5. Replace the radiator cap.

E. Test the coolant recovery system.

CAUTION: Road test a vehicle only with the instructor'spermission.

1. Drive the vehicle for several miles.


3. Observe the level in the coolant recovery tank.

4. Allow the cooling system to completely cool down.


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5. Remove the radiator cap and check the coolant level. Theradiator should be completely full and the level in the coolantrecovery tank should have dropped.

6. Inspect the coolant recovery system if a problem is found.

a. Inspect the hose and hose connections between theradiator and the coolant recovery tank.

b. Inspect the coolant recovery tank for damage.

c. Inspect the radiator cap gasket and valve.

F. Service the cooling system.

1. Replace the radiator cap if it is damaged or has a bad rubberor metal seal. Lock the new radiator cap onto the radiatorfiller neck.

2. Replace hoses that are damaged, worn, or show deterioration.Replace the spring on the lower radiator hose that prevents thewater pump from sucking the hose shut.

3. Remove and install the radiator.

NOTE: Procedures for removing and installing the radiatorvary significantly. Consult the appropriate service informationto obtain the correct procedures. The following are generalprocedures.

a. Remove the radiator.

1. Drain the cooling system.

2. Disconnect the hoses and oil cooler lines.

3. Remove the radiator mounts (brackets).

4. Remove the shroud/electric fan assemblies.

5. Remove the electrical connectors.

6. Remove the radiator.

b. Install the new radiator.

1. Position the new radiator in the vehicle.


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2. Connect the electrical connectors.

3. Install the fan shroud/electrical fan assemblies.

4. Install the radiator mounts.

5. Connect the hoses and oil cooler lines.

6. Refill the cooling system.

4. Remove and install the coolant recovery tank.

a. Remove the mounting brackets.

b. Remove the coolant recovery tank.

c. Position the new coolant recovery tank in the vehicle.

d. Connect the mounting brackets. Tighten as necessary.

G. Drain, flush, and refill the cooling system.

1. Remove the radiator cap. Make sure the petcock, located onthe bottom radiator tank, can open freely.

2. Remove the thermostat housing and the thermostat. Clean themating surfaces of the thermostat housing and the engine toremove the old gasket/seal.






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6. Open the petcock, allowing the coolant to drain completelyfrom the radiator.

CAUTION: Used coolant is classified as toxic waste andmust be disposed of according to law.

7. Remove one of the heater hoses and connect a supply of freshwater to the hose end that leads into the heater.

NOTE: Chemical cleaners are available for cleaning a dirtysystem. These circulate through the system to remove dirt anddebris. Follow package directions when using these cleaners.

8. Allow the cooling system to fill.

9. When the system is full, start the engine and allow it to idle.

10. Adjust the water flow so that the radiator stays full while thedrain is running wide open. Keep the engine and the freshwater running until the discharge fluid runs clear.

11. Shut off the engine. Let the drain run until it stops and thenclose the petcock.

12. Install the thermostat with the wax-filled pellet toward theinside of the engine. Center the thermostat in the housing.Install the new gasket/seal and thermostat housing. Use thecorrect sealer to install the gasket.

13. Reconnect the heater hose.

14. Consult service information to select the correct coolant anddetermine the coolant capacity for the vehicle.

15. Using the correct coolant capacity, measure coolant at half thiscapacity and add to the radiator. Pour the coolant down theradiator filler neck.


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16. Continue to fill the radiator with clean, fresh water. Fill toproper specifications.

17. Start the engine and allow it to reach normal operatingtemperature. The coolant should start to circulate and theupper radiator tank should become warm. Bleed the system, ifnecessary.

18. If the cooling system is working properly, top off the radiatorwith clean water and replace the radiator cap.


V. Procedures for verifying correct camshaft timing

A. Verify correct camshaft timing with the valve timing componentslocated in the block (nonoverhead camshaft engines).

1. Disassemble the engine sufficiently to observe the valves in thenumber 1 cylinder. Disassembly may require removing therocker arm cover from the head.

2. Find the timing mark on the harmonic balancer, which islocated at the front of the engine crankshaft.

3. Rotate the engine in the normal direction. Observe the actionof the valves in the number 1 cylinder.

a. Find the overlap position of the cylinder by noting whenthe exhaust valve closes and when the intake valvebegins to open.

NOTE: The overlap position occurs when both of thevalves are slightly open at the same time (one just comingclosed and the other just coming open).

b. Position the crankshaft so that the valves are in theoverlap position. At this position, the timing marksshould be at top dead center (TDC). If they are not, thevalve timing is off. The engine short block must bepartially disassembled to correct this problem.

5. Inspect the condition of the timing chain and sprockets.

a. Remove the distributor cap. Rotate the crankshaft andobserve the distributor rotor.


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b. Stop rotating the crankshaft when there is movement ofthe distributor rotor.

c. Use chalk to mark the location of the distributor rotorand the crankshaft.

d. Begin to rotate the engine backwards and observe thedistributor rotor.

e. Stop rotating the crankshaft when the distributor rotormoves. Record the amount of crankshaft rotationrequired to start movement of the distributor rotor, whichis a sign of timing chain looseness. Replace timingcomponents if the movement is more than 3/4 in.

B. Verify correct camshaft timing in overhead camshaft engines.

NOTE: Overhead camshaft engines use timing chains or belts todrive the camshaft(s). These can use one or more camshafts. Besure to time all of the components correctly.

1. Turn the crankshaft to the TDC position.

2. Remove the camshaft drive cover so that the camshaft(s) andtiming marks can be seen.

NOTE: Some camshaft drive covers have small openings thatcan be used to see the timing marks without removing thecover.

3. If the timing marks are correctly aligned, inspect the conditionof the camshaft drive chain or belt and gears.

4. If the timing marks are not correctly aligned, time according tomanufacturer’s procedures. Make sure to determine the causeof the incorrect timing condition, such as a worn timing belt,timing chain, gear, or tension.


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UNIT III: COMPUTERIZED ENGINE CONTROLS DIAGNOSIS ANDREPAIR


I. Unit objective

II. Lesson plans

A. Lesson 1: Introduction to Computerized Engine Controls


2. Assignment Sheet

a. AS1-L1-UIII: Computerized Engine Controls

b. Answers to the assignment sheet

B. Lesson 2: On-board Diagnostics and Driveability


2. Job sheets

a. JS1-L2-UIII: Obtain and Interpret Diagnostic TroubleCodes and Scan Tool Data

b. JS2-L2-UIII: Diagnose the Causes of Emissions orDriveability Concerns Using Stored Diagnostic TroubleCodes

c. JS3-L2-UIII: Diagnose the Causes of Emissions orDriveability Concerns with No Stored Diagnostic TroubleCodes

d. JS4-L2-UIII: Check for Module Communication Errors

C. Lesson 3: Test and Service Computerized Engine ControlComponents



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2. Job sheets

a. JS1-L3-UIII: Test and Service Computerized EngineControls Using a Digital Multimeter

b. JS2-L3-UIII: Test and Service Computerized EngineControls Using a Scan Tool

c. JS3-L3-UIII: Test and Service Computerized EngineControls Using a Graphing Multimeter/Digital StorageOscilloscope

III. Unit III Test


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UNIT OBJECTIVE

After completing this unit, students should be able to diagnose and repaircomputerized engine controls. Students will demonstrate mastery of thematerial by completeing the assignment sheet, successfully performing specifictasks on the job sheets, and achieving a score of on the Unit III Test.

SPECIFIC OBJECTIVES


Lesson 1

I. Describe the basic operation of computerized engine controls.

II. Discuss the basics of computers.

III. Identify and describe the types of sensors.

IV. Identify and describe the types of actuators.

V. Discuss the basics of on-board diagnostic systems.

VI. Complete the assignment sheet on computerized engine controls(AS1-L1-UIII).

Lesson 2

I. Explain the procedures for obtaining and interpreting diagnostic troublecodes and scan tool data.

II. Explain the procedures for diagnosing the causes of emissions ordriveability concerns using stored diagnostic trouble codes.

III. Explain the procedures for diagnosing the causes of emissions ordriveability concerns with no stored diagnostic trouble codes.

IV. Explain the procedures for checking for module communication errors.


A. Obtain and interpret diagnostic trouble codes and scan tool data(JS1-L2-UIII).


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B. Diagnose the causes of emissions or driveability concerns usingstored diagnostic trouble codes (JS2-L2-UIII).

C. Diagnose the causes of emissions or driveability concerns with nostored diagnostic trouble codes (JS3-L2-UIII).

D. Check for module communication errors (JS4-L2-UIII).

Lesson 3

I. Explain the procedures for testing wiring and wiring circuits.

II. Explain the procedures for testing and servicing sensors.

III. Explain the procedures for testing and servicing actuators.

IV. Explain the procedures for testing computerized engine controls using agraphing multimeter or digital storage oscilloscope.


A. Test and service computerized engine controls using a digitalmultimeter (JS1-L3-UIII).

B. Test and service computerized engine controls using a scan tool(JS2-L3-UIII).

C. Test and service computerized engine controls using a graphingmultimeter/digital storage oscilloscope(JS3-L3-UIII).


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LESSON 1: INTRODUCTION TO COMPUTERIZED ENGINECONTROLS

I. Basic operation of computerized engine controls

A. Computerized engine controls are highly complex and involve manyinterrelated components. System design, testing, and servicingprocedures vary greatly depending on the manufacturer.

1. Sensors input information to the powertrain control module(PCM), which uses the input to manipulate the output devices,or actuators. Through this process, the PCM maintainsefficient engine operation.

2. Computerized engine controls use different sensors to relayinformation about engine load, engine speed, air/fuel mixture,and engine temperature.

3. The PCM makes output decisions that alter system operation.Alterations include adjusting ignition timing, changing engineidle speed, adjusting the air/fuel mixture, altering operation ofemissions systems, and controlling transmission/transaxleoperation.

II. Basics of computers

A. In addition to the PCM, a vehicle uses one or more computers tocontrol various systems. The PCM receives and processes data fromthe various computers for overall monitoring and control of theengine, transmission, and other systems.

1. The heating and air conditioning computer controls theoperation of the heating and air conditioning system.

2. The engine control computer controls engine function.


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3. The suspension computer modifies ride stiffness and shockabsorber action.

4. The ignition control module controls ignition timing, sparkplug firing, and ignition coil pack operation.

5. The instrumentation computer operates dashboard displays.

6. The anti-lock brake (ABS) computer receives information fromspeed sensors in each of the wheels. The computer thenapplies and releases the brakes so the vehicle can stop withoutlocking the wheels.

7. The body control computer provides memory and otherfunctions for the electrical convenience accessories, such as theradio and driver information center.

B. Computers receive data input, interpret and process the data input,and then produce data output that affects electronic or mechanicalcomponents.

1. Computers use digital signals and must convert analog signalsto digital signals.

a. An analog signal varies in strength across a continuumand is measured by needle swings or bar movement. Theneedle indicates smooth progression of the rise or fall ofvoltage.


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b. A digital signal does not vary in strength. It is either onor off. These are expressed as numerical readouts.

C. Computers use many components.

1. The voltage regulator converts higher voltage to lower voltagefor use by the computer and sensors.

2. The amplifiers increase lower voltage to higher voltage for useby internal computer components.

3. The conditioners convert incoming analog signals to digitalsignals and outgoing digital signals to analog signals.

4. The buffer is a temporary storage area for data.

5. The microprocessor makes calculations and decisions for thecomputer.

6. Memory is the circuit that stores data for the microprocessor.

a. Random access memory (RAM) is for temporary datastorage. The microprocessor reads RAM and writes datainto RAM. When the computer is shut off or loses power,RAM data is erased.

b. Read only memory (ROM) is for long-term data storage.The microprocessor cannot write information into theROM.

c. Programmable read only memory (PROM) containsinformation about the specific vehicle, such as thenumber of engine cylinders and fuel system type.

d. Erasable programmable read only memory (EPROM)contains semipermanent data, such as mileage readingsfor an electronic dash display. EPROM can bereprogrammed through a difficult process that involvesthe manufacturer using special equipment.


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e. Electrically erasable programmable read only memory(EEPROM) or flash erasable programmable read onlymemory (FEPROM) can be reprogrammed by atechnician in the field without erasing the entire PROM.Operating limits can easily be changed if there areperformance or driveability problems.

f. Keep alive memory (KAM) contains information thatallows the vehicle to continue to run even if it receivesabnormal sensor input.

7. The clock produces a steady pulse that coordinates computeractivities.

8. The output drives power transistors that convert lower voltageto higher voltage for use by the actuators.

9. The circuit board connects and holds computer components.

10. The harness connector is a multipin terminal that connectssensor and actuator wires.

11. The computer housing contains computer components.

III. Types of sensors

NOTE: Computerized engine controls vary; some systems use moresensors than others. New sensor types are being developed and added tosystems while other sensor types are finding less use.

A. The permanent magnet signal generator can be a crankshaftposition (CKP) sensor, distributor shaft position sensor, camshaftposition (CMP) sensor, and vehicle speed sensor (VSS). The PCMuses alternating current (AC) signals from permanent magnet signalgenerators to establish ignition timing and monitor vehicle speed.

NOTE: In some cases, the CKP sensor, distributor shaft positionsensor, and CMP sensor are Hall-effect sensors. Check the wiring todetermine the type of sensor. A permanent magnet signal generatoruses two wires; a Hall-effect sensor uses three wires.

1. A permanent magnet signal generator produces an AC signalto monitor speed and position of moving parts. It induces ACin a conductor by passing a magnetic field through it.

a. The sensor uses small teeth, or reluctors, mounted on thedistributor shaft, crankshaft, or camshaft.


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b. A magnetic pickup coil that does not move is mountedclose to the moving part. The reluctors on the shaft comeclose to, but do not touch, the pickup coil.

c. As a reluctor tooth on the moving shaft approaches thepickup coil, a magnetic field moves across the pickup coilwinding and produces positive voltage.

d. As the shaft rotates, the reluctor tooth aligns with thepickup coil and the magnetic field is eliminated, causingvoltage to fall to zero. The first part of the AC cycle iscomplete.

e. When the reluctor moves away from the pickup coil, themagnetic field is induced again, causing negative voltageto be produced.

f. Finally, the reluctor moves clear of the pickup coil andvoltage returns to zero. This movement from positive tonegative voltage represents one AC cycle.

2. A permanent magnet signal generator provides an accurateindication of both shaft speed and position. The faster theshaft turns, the more AC cycles per second produced.

a. Along with a reference notch to indicate shaft position,there is usually one reluctor for every two pistons. Theposition of each reluctor is coordinated with the positionof the piston pairs.

b. By monitoring reluctor position, the PCM knows whenone of the pistons in the pair is in the combustion strokeand when the other is in the exhaust stroke.

c. The speed and position of the crankshaft and distributorshaft are closely related to piston speed and position.

3. The VSS monitors vehicle speed and is mounted on thetransmission where the speedometer cable drive gear islocated. The VSS sends a signal to the PCM proportional tovehicle speed, allowing the PCM to control transmissionshifting and torque converter operation.

NOTE: The CKP sensor sometimes functions as the VSS.


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B. The Hall-effect sensor monitors the speed of moving parts. The CKPsensor or CMP sensor can be Hall-effect sensors.

1. The Hall-effect sensor is mounted on the distributor shaft orthe crankshaft. It determines piston position and engine speedand establishes ignition timing.

2. The Hall-effect sensor has a thin, wafer-like semiconductor.Current is constantly applied to the semiconductor. Acrossfrom the semiconductor is a permanently-mounted magnet.The semiconductor is "invaded" by the magnetic field.Depending on the application, the semiconductor and magnetare mounted close to the shaft.

3. The shaft is equipped with a trigger wheel. Metal shutters aremounted on the trigger wheel and are designed to passbetween the semiconductor and magnet as the shaft turns.

4. When there is no shutter between the semiconductor andmagnet, the magnetic field invades the semiconductor fieldand disturbs current flow through the semiconductor. Thisproduces a weak voltage signal called Hall voltage.


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5. When a shutter is between the semiconductor and magnet, thesemiconductor is shielded from the magnetic field. The steadycurrent flows in one side of the semiconductor and out theother. Hall voltage is not sent to the PCM.

6. Hall voltage is sent to a control unit. The voltage switches offthe control unit and breaks the circuit to the ignition coil. Thisfires the ignition coil.

7. As another shutter interrupts the magnetic field, the steadycurrent flow returns to normal and Hall voltage is eliminated.The control unit is then switched on and reenergizes theignition coil, making it ready to fire again.

C. The engine coolant temperature (ECT) sensor monitors enginecoolant temperature and indicates engine temperature. Variationsin engine temperature require changes be made to the richness ofthe air/fuel mixture.

1. The ECT sensor is a thermistor, a sensor that varies resistanceaccording to temperature.

2. A reference voltage signal of approximately 5 volts is sent fromthe PCM to the ECT sensor and then returned to the PCM.

3. The ECT sensor is designed to change resistance according totemperature. Most ECT sensors have a negative resistance-to-temperature relationship. As the temperature goes up, theresistance goes down. The reverse is also true. As thetemperature goes down, the resistance goes up.

4. The ECT sensor is mounted immersed in engine coolant. Asthe engine coolant temperature goes down, ECT sensorresistance goes up.


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a. Resistance may be as high as 27 K ohms when the enginecoolant is 68°F. If reference voltage of 5 volts is sent tothe ECT sensor, a voltage drop of 3 volts results. Thisleaves approximately a 2-volt signal to return to thePCM.

b. Resistance may be as low as 2 K ohms when the enginecoolant is 212°F. If reference voltage of 5 volts is sent tothe ECT sensor, a voltage drop of .5 volts results. Thisleaves approximately a 4.5-volt signal to return to thePCM.

5. The PCM interprets variations in the return voltage signal asvariations in engine coolant temperature. The PCM thenincreases or decreases engine idle or alters the air/fuel mixtureto ensure maximum engine efficiency at various temperatures.

D. The intake air temperature (IAT) sensor monitors temperature ofincoming air. Variations in air temperature require changes bemade to the richness of the air/fuel mixture.

NOTE: Engines that use a mass airflow sensor usually do not usean IAT sensor.


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1. The IAT sensor is a thermistor.

2. A reference voltage signal of approximately 5 volts is sent fromthe PCM to the IAT sensor and returned to the PCM.

3. The IAT sensor is designed to change resistance according totemperature. Most IAT sensors have a negative resistance-to-temperature relationship. As the temperature goes up, theresistance goes down. The reverse is also true. As thetemperature goes down, the resistance goes up.

4. The IAT sensor is mounted in the engine air inlet duct, whichis often in the intake opening of the mass airflow sensor. Airentering the engine flows over the IAT sensor. As thetemperature of the air entering the engine goes down, IATsensor resistance goes up.

a. Resistance may be as high as 27 K ohms when the airtemperature is 68°F. If reference voltage of 5 volts is sentto the IAT sensor, a voltage drop of 3 volts results. Thisleaves approximately a 2-volt signal to return to thePCM.

b. Resistance may be as low as 2 K ohms when the airtemperature is 212°F. If reference voltage of 5 volts issent to the IAT sensor, a voltage drop of .5 volts results.This leaves approximately a 4.5-volt signal to return tothe PCM.

5. The PCM interprets variations in the return voltage signal asvariations in the temperature of air entering the engine. ThePCM then increases or decreases engine idle or alters the air/fuel mixture to ensure maximum engine efficiency at varioustemperatures.

E. The throttle position (TP) sensor monitors throttle position, or howfar the throttle plate is open. The PCM alters the air/fuel mixture oradvances/retards ignition timing based on input from the TP sensor.


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1. The TP sensor is a potentiometer, a device that variesresistance according to the movement of mechanical parts.The TP sensor is designed to vary resistance according tothrottle movement.

a. The TP sensor has three electrical connections. There isone connection at the end of each resistance unit and oneat the end of the wiper arm.

b. The wiper arm is attached to the throttle. As the throttlemoves, the wiper arm moves across the resistance unit.

c. The PCM sends reference voltage of 5 volts to the TPsensor. The wiper arm movement varies resistance,increasing or decreasing voltage drop across theresistance unit. This increases or decreases the voltagesignal returned through the wiper arm circuit to thePCM.

d. When the throttle is at idle, the position of the wiper armresults in high resistance, creating a high voltage drop ofapproximately 4.5 volts in the TP sensor. This allows a.5-volt signal to return to the PCM, indicating the engineis at idle.

e. When the throttle is at the wide open position, theposition of the wiper arm results in low resistance,creating a low voltage drop of approximately .5 volts inthe TP sensor. This allows a 4.5-volt signal to return tothe PCM, indicating the engine is at the wide openposition.

f. Some vehicles use a throttle position switch that indicateswhen the throttle is closed or wide open.

F. The manifold absolute pressure (MAP) sensor monitors the absolutepressure in the intake manifold and indicates engine load.


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NOTE: In some vehicles, a barometric pressure (BARO) sensormonitors barometric pressure. It functions and is serviced like theMAP sensor. Since the late 1980s, most manufacturers combine thissensor with the MAP sensor.

1. Manifold absolute pressure is determined by measuringvacuum. The higher the vacuum is, the lower the pressure is.

a. Absolute pressure is a pressure reading that includesatmospheric pressure. Regular pressure readings do notinclude atmospheric pressure.

1. Atmospheric pressure is 14.7 pounds per squareinch (psi) at sea level. An absolute pressure readingof 14.7 psi registers as zero on a regular pressuregauge.

b. Absolute pressure in the intake manifold indicates engineload and speed. The MAP sensor is located in the intakemanifold to monitor intake manifold pressure. It sendsinformation to the PCM, and then adjustments are madeto ignition timing.

2. The MAP sensor receives reference voltage of 5 volts from thePCM. The MAP sensor alters the signal in relation to intakemanifold pressure and then returns the altered signal to thePCM, indicating engine load and barometric pressure.

3. There are two basic types of MAP sensors. The first is thefrequency-signal type that sends a frequency hertz (Hz) signalto the PCM. The second is the simple-voltage type that sends avoltage signal to the PCM.

a. The frequency-signal type receives reference voltage fromthe PCM. The MAP sensor converts the reference voltageinto a frequency signal. The MAP sensor return signal isthen measured in Hz.


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1. The following graph shows inches of mercury (inHg), kilopascals (kPa), and Hz specifications for thefrequency-signal type.

2. During periods of low manifold pressure, or highvacuum, the MAP sensor sends a return low-frequency signal as low as 80 Hz to the PCM. Lowmanifold pressure indicates light engine load.

3. During periods of high manifold pressure, or lowvacuum, the MAP sensor sends a return high-frequency signal as high as 159 Hz to the PCM.High manifold pressure indicates heavy engineload.

b. The simple-voltage type varies resistance in reaction tomanifold pressure, or manifold vacuum. The MAPsensor alters the reference voltage returning to the PCM.

1. When manifold pressure is high, or low vacuum,MAP sensor resistance decreases, creating a lowvoltage drop across the MAP sensor. A relativelyhigh voltage signal is returned to the PCM.

2. When manifold pressure is low, or high vacuum,MAP sensor resistance increases, creating a highvoltage drop across the MAP sensor. A relativelylow voltage signal is returned to the PCM.

G. The mass airflow (MAF) sensor monitors the mass of air entering theintake manifold. The PCM uses the information about airflow tomodify ignition and fuel system operation. Most vehicles that use aMAF sensor do not use an IAT sensor.


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H. The volume airflow (VAF) sensor monitors the amount of airentering the engine. It is a hinged vane in the airstream that swingsopen when pushed by the air that is drawn into the engine throughthe throttle valve.

I. The oxygen sensor (O2S) monitors the amount of oxygen in theexhaust and indicates the richness or leanness of the air/fuelmixture.

J. The knock sensor (KS) monitors the engine for knock or ping. Itsends a “yes” or “no” signal to the PCM, which then retardsignition timing until the “yes” signal stops.

IV. Types of actuators

A. The PCM takes sensor input and alters the function of the engine orrelated systems. The PCM uses actuators to control componentfunction. Actuators can be located almost anywhere on a vehicle.

B. The solenoid opens or closes valves that control vacuum to systems,such as the air injection system. On some vehicles, the solenoidoperates fuel injectors and controls throttle position.

1. The solenoid consists of a metal core and windings.


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2. The PCM activates the solenoid by grounding the solenoidcircuit. When the solenoid is activated, current creates amagnetic field around the coil windings. This magnetic fieldpulls the metal core into the coil windings.

3. The action of the metal core opens and closes passages thatcarry vapor, vacuum, or fluid. It also moves other mechanicalcomponents or makes electrical connections.

4. The PCM activates the solenoid coil very rapidly, causing themetal core to move rapidly, in some cases, hundreds of timesper second. This allows very precise control of vapor, vacuum,or fluid.

C. Relays are used when a high current load needs to be controlled bythe PCM. The PCM grounds the coil windings and then the coilmagnetic field pulls the contacts closed, allowing large current flowto the load.

D. A servo motor is another actuator. The PCM grounds the servomotor circuit to shut off the servo motor. When necessary, it alsoreverses servo motor rotation.

E. The ignition module contains the transistor that drives the coilprimary. The PCM uses sensor input to fire the ignition coil at theproper time.

V. Basics of on-board diagnostic systems

A. On-board diagnostic (OBD) systems are a self-test feature built intoall new vehicles. These are designed to detect problems and indicatewhere the problems might be located. The PCM scans the input andoutput information to detect incorrect voltage, resistance, or current.


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1. A scan tool communicates with the OBD system to check fordiagnostic trouble codes (DTCs) relating to the malfunctioningsystem.

a. The scan tool snapshot is an immediate reading of theoperating parameters present when a problem occurs.Snapshot information is used if a problem is difficult tofind or if the problem is intermittent. This is used when aDTC is present.

b. The scan tool datastream values are live electrical valuesmeasured when the engine is running or the vehicle isdriven. The datastream values are used if there is anengine performance problem and no DTCs are set.Values almost out of specifications may indicate aproblem area.

2. The on-board diagnostics generation one (OBD I) system is theearly version of these types of systems.

a. OBD I stores DTCs and turns on a dash light when amalfunction occurs.

b. OBD I cannot determine the sort of problem occurringwith a sensor or system.

3. The on-board diagnostics generation two (OBD II) system isdesigned to monitor how efficiently the vehicle’s systems areoperating. Also, OBD II helps to keep vehicles runningefficiently for at least 100,000 miles.


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a. OBD II monitors each sensor and has provisions formonitoring fuel trim and fuel tank pressure. The PCMmonitors each system continuously for compliance withemissions standards.

B. When the OBD system detects an engine problem, it stores a DTC(s)in the PCM for later retrieval. When checking the DTC(s) using ascan tool, the DTC(s) appears in a digital readout format.

1. There are two types of DTCs.

a. A hard DTC indicates a problem that is always present,such as a broken linkage on a potentiometer. Regardlessof conditions, the DTC does not go away.

b. A soft DTC indicates a problem that occurs only undercertain conditions. For example, a very small break in awire can cause an open circuit that occurs only duringroad shock.

1. The soft DTC is usually stored for a limited time. Insome instances, the soft DTC will not be stored.

2. The technician must try to reproduce the conditionsthat caused the soft DTC during diagnosis.

2. An engine can have more than one problem that results inseveral different DTCs.

a. Computerized engine control systems have interrelatedsystems and components. A problem in one can trigger aproblem in another.

b. Check service information to determine which DTCshould be addressed first.

3. Some DTCs refer to specific sensors and others refer to generalconditions, such as an overly rich air/fuel mixture. Thediagnostic steps for the two types of DTCs are different.

4. The cause of a DTC can be mechanical problems, faulty wiringand connections, a faulty sensor or actuator, and/or a faultyPCM.


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LESSON 2: ON-BOARD DIAGNOSTICS AND DRIVEABILITY

NOTE: Most often engine performance concerns are mechanical and do notinvolve the computerized engine controls. Eliminate possible mechanicalsolutions before conducting an in-depth electronic diagnosis. The concerncould be much more basic than it first appears.

I. Procedures for obtaining and interpreting diagnostic trouble codes andscan tool data

A. The first step in diagnosing computerized engine controls is toobtain and interpret diagnostic trouble codes (DTCs) and other scantool data. This information is a valuable resource to the technicianbecause it can provide a starting point for diagnosis. From the scantool data, the technician can then use available service informationand their own knowledge to further diagnosis and/or begin therepair process.

B. Obtain and interpret DTCs and scan tool data.

1. Determine if the system uses on-board diagnostics generationone (OBD I) or on-board diagnostics generation two (OBD II).

2. Connect the scan tool to the data link connector (DLC).

3. Check the digital reading and record stored DTCs.

4. Check the datastream information. Compare to themanufacturer’s specifications.

5. Check and record stored snapshot information.

6. Using available service information, interpret the scan tooldata.

7. When applicable, clear the codes.

8. Disconnect the scan tool.


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II. Procedures for diagnosing the causes of emissions or driveability concernsusing stored DTCs

A. Stored DTCs can make the diagnosis and repair process easier,because the technician has a set starting point. A hard DTC makesthe process much quicker than a soft DTC.

B. Diagnose the causes of emissions or driveability concerns usingstored DTCs.


2. Connect the scan tool to the DLC.


4. Check and record stored snapshot information.

5. Check the datastream information for sensor output andactuator operation relating to the DTCs or driveabilityconcerns. Record abnormal readings.

6. With the scan tool, test for malfunction of interrelated systems.Make sure to test the cruise control, security system,suspension controls, traction controls, heating and airconditioning systems, automatic transmission, accessories notinstalled by the original manufacturer, and other similarsystems particular to the vehicle.

7. Using available service information, interpret the scan tooldata. Determine necessary action to correct the emissions ordriveability concern.

8. When applicable, clear the DTCs.


III. Procedures for diagnosing the causes of emissions or driveability concernswith no stored DTCs

A. When no DTC is stored, the technician must isolate the cause of theconcern using symptom-based troubleshooting. Even if a DTC is notstored, technicians can still use the datastream information to helpisolate the cause of the concern.


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B. Diagnose the causes of emissions or driveability concerns with nostored DTCs.


2. Connect the scan tool to the DLC.

3. Check the digital reading. If the vehicle has stored DTCs, seeSection II.B to continue diagnosis.

4. Check the datastream information for sensor output andactuator operation relating to the DTCs or driveabilityconcerns. Record abnormal readings.

5. Using available service information, interpret the datastreaminformation.


7. Based on the datastream information and the followingproblems and causes, determine necessary action to correct theemissions or driveability concern.

a. The engine cranks but does not start. Possible causes areas follows.

• Charcoal canister full of fuel• Defective mass airflow (MAF) sensor or manifold

absolute pressure (MAP) sensor• Malfunctioning engine coolant temperature (ECT)

sensor or circuit• Exhaust gas recirculation (EGR) valve stuck open• Defective charcoal canister vent valve• Inadequate fuel pressure• Empty fuel tank• Water in the fuel supply• Nonfunctioning cold start fuel injector• Severely-restricted fuel injectors


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b. The engine is hard to start when hot. Possible causes areas follows.

• Clogged air filter• Positive crankcase ventilation (PCV) valve stuck

open• Vacuum leak• Malfunctioning ECT sensor or circuit• Malfunctioning intake air temperature (IAT) sensor

or circuit• Defective MAF sensor or MAP sensor• Malfunctioning throttle position (TP) sensor or

circuit• No fuel pressure or inadequate fuel pressure• Leaking or continuously operating cold start valve

c. The engine starts but does not run. Possible causes are asfollows.

• Defective charcoal canister vent valve• EGR valve stuck open• Intake manifold vacuum leak• Insufficient fuel flow

d. The engine idles erratically or rough when cold or atnormal operating temperature. Possible causes are asfollows.

• Dirty throttle plate or bore• Minimum idle speed adjustment out of specification• EGR valve stuck open or leaking• Vacuum leak• Air leak in the intake duct and/or intake manifold• Defective or malfunctioning idle system• Lean or rich air/fuel mixture in the fuel injectors• Insufficient fuel pressure from the fuel pump• Malfunctioning TP sensor or circuit• Clogged fuel filter or impurities in the fuel supply• Malfunctioning cold start fuel injector

e. There is an excessively high idle speed. Possible causesare as follows.

• Vacuum leak• Sticking throttle linkage• Incorrectly adjusted idle speed


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f. The engine misses throughout the driving speed range.Possible causes are as follows.

• Clogged fuel filter or impurities in the fuel supply• Insufficient fuel pressure from the fuel pump• Vacuum leak• Leaking EGR valve• Lean air/fuel mixture in the fuel injectors

g. There is engine hesitation and/or stumbling and stallingupon acceleration. Possible causes are as follows.

• Clogged fuel filter• Malfunctioning TP sensor or circuit• Malfunctioning IAT sensor or circuit• Malfunctioning MAP sensor or circuit• Dirty throttle plate or bore• Insufficient fuel pressure from the fuel pump• Lean air/fuel mixture in the fuel injectors

h. The engine lacks power or has sluggish performance.Possible causes are as follows.

• Clogged air filter• Restriction in the exhaust system• Vacuum leak• Heat control valve stuck open during cold engine

operation or stuck closed during warm engineoperation

• Malfunctioning MAP sensor or circuit• Clogged fuel filter or impurities in the fuel supply• Lean air/fuel mixture in the fuel injectors

i. The engine stalls on deceleration or when coming to aquick stop. Possible causes are as follows.

• EGR valve stuck open or leaking around the base• Incorrectly adjusted idle speed• Incorrectly adjusted or bad TP sensor• Incorrectly adjusted or malfunctioning idle speed

control (ISC) or electronic air control valve• Clogged fuel filter or impurities in the fuel supply• Vacuum leak


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j. There is surging at a steady speed. Possible causes are asfollows.

• Clogged air filter• Vacuum leak• Air leak in the intake duct and/or intake manifold• EGR valve stuck open or leaking around the base• Malfunctioning oxygen sensor (O2S) or circuit• Malfunctioning TP sensor or circuit• Malfunctioning MAF sensor or circuit• Malfunctioning MAP sensor or circuit• Loose fuel injector wiring harness connectors• Insufficient fuel pressure from the fuel pump• Defective fuel pump• Lean air/fuel mixture in the fuel injectors• Defective powertrain control module (PCM) or

information sensor

k. When shut off, the engine idles too fast or diesels.Possible causes are as follows.

• Vacuum leak• Malfunctioning EGR valve• EGR valve stuck closed• Heat control valve stuck closed• Idle speed too high• Excessive engine operating temperature• Malfunctioning fuel shutoff system

l. There is backfiring through the intake or exhaust.Possible causes are as follows.

• Vacuum leak in the PCV or charcoal canister purgeline

• Vacuum leak at the fuel injectors, intake manifold,air control valve, or vacuum lines

• Malfunctioning EGR system


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m. There is poor fuel economy. Possible causes are asfollows.

• Clogged air filter• Heat control valve stuck open or closed• PCV valve stuck open or closed• Dirty PCV filter• Defective O2S• Incorrectly adjusted idle speed• Fuel leak• Worn or damaged internal parts in the electronic

fuel injection (EFI) system• Malfunctioning cold start fuel injector

n. There is knock, or ping. Possible causes are as follows.

• Nonfunctioning EGR valve• Vacuum leak

o. The exhaust smoke is black. Possible causes are asfollows.

• Rich air/fuel mixture• Dirty air filter• Restricted intake duct

p. There is a fuel smell. Possible causes are as follows.

• Overfull fuel tank• Fuel tank cap gasket not sealing properly• Leaking fuel lines• Fuel injectors stuck open• Fuel injectors leaking internally or externally• Clogged charcoal canister filter• Vapor leaks from the evaporative emissions control

(EVAP) system lines

IV. Procedures for checking for module communication errors

A. In-vehicle data traffic is growing rapidly. Traditionally, individualwiring harnesses were used for data transfer between control unitsand sensors or display devices. As the number of control units andassociated devices increased, the number of wiring harnesses andrequired interconnections increased.

1. Some modern vehicles contain three miles of wiring cable. Theweight of the cable presents a problem.


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2. Another problem arises from the complexity of the wiring.Making minor changes and diagnosing faults can be extremelydifficult.

B. A bus network is the most effective way to deal with the wiringissues. A bus network is a transmission path on which signals aredropped off or picked up at every device attached to the line.

1. There are four categories of in-vehicle bus networks.

a. The body control bus handles the dashboard andinstrument panel displays, mirrors, seat belts, door locks,and passive airbags.

b. The entertainment and driver-information systems bushandles the radios, Internet browsers, CD/DVD players,telematics, and other entertainment systems.

c. The under the hood bus handles the antilock brakes,emissions control systems, powertrain, and transmissionsystems.

d. The advanced safety systems bus handles the brake-by-wire, steer-by-wire, and driver assistance systems.

2. There are different types of in-vehicle bus networks.

a. A local area network (LAN) minimizes the use ofindividual wiring harnesses for data exchanges andreduces the required interconnections. An in-vehicleLAN must have minimum signal delays betweencomponents to ensure error-free data transfer.

b. A controller area network (CAN) is currently thestandard for in-vehicle bus networks. A typical vehicleintegrates two or three CAN buses. A high-speed CANbus runs the critical functions, such as engine control andantilock brakes.

c. The local interconnect network (LIN) supplements theCAN. It is an inexpensive bus that enablescommunication for sensors and actuators where thebandwidth of a CAN is not required, such as doorcontrol and climate regulation.


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C. U codes are DTCs assigned to the bus network. These codes followthe same format as powertrain codes. The U prefix indicatesnetwork communication errors.

1. Individual LAN and CAN bus modules are capable of settingU codes when they detect abnormal conditions. Most busmodules are able to detect conditions, such as bus failure orloss of communication with one or more modules.

2. Some CAN bus modules contain a system basis chip capable ofmonitoring the actual conditions on the bus circuits. Thesemodules can set additional DTCs for conditions, such asvoltage high, voltage low, shorted bus circuits, or open buscircuits.

3. DTC status is common to all modules. The DTC is active if theconditions currently exist. The DTC is stored if the conditionno longer exists.

D. Check for module communication errors.

1. Connect the scan tool equipped with LAN and CAN capabilityto the DLC. If necessary, enter vehicle information.

2. Set the scan tool to check for LAN and CAN DTCs. Thisallows the scan tool to communicate with all modules forerrors.


NOTE: Some vehicles provide the scan tool with a report thatmay include the module name, part number, hardware andsoftware version, diagnostic version, DTCs, description of theDTCs, DTC status (active or stored), accumulated timer,ignition cycle counter, and mileage when DTCs were set.

4. Using available service information, interpret the scan tooldata. Determine necessary action to correct modulecommunication errors.

5. When applicable, clear the DTCs.



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LESSON 3: TEST AND SERVICE COMPUTERIZED ENGINECONTROL COMPONENTS

I. Procedures for testing wiring and wiring circuits

A. Check the reference voltage to the sensors using a digital multimeter(DMM).

1. Locate the sensor to be tested. Note the wire colors running tothe sensor.

2. Determine the wire that carries reference voltage from thepowertrain control module (PCM) to the sensor, the wire thatreturns the voltage signal, and the wire that grounds thesensor.

NOTE: Technicians must be able to read and interpret wiringdiagrams because the labelling of wiring varies bymanufacturer.

a. The ground wire, labelled GND, is usually black with ablue stripe.

b. The wire that carries the voltage signal back to the PCM,labelled TP, is usually light green with a white stripe.

3. Select the direct current (DC) voltage function on the DMMand set to the proper range.

4. Connect the red probe to the harness connector of thereference voltage wire and the black probe to the negativebattery cable.

5. Check the reading. Compare to manufacturer’s specifications.If reference voltage is nonexistent or not within specifications,check for loose or corroded wire connections back to the PCM.If the connections are not loose or corroded, check thecontinuity of the reference voltage wiring back to the PCM.

6. Disconnect the DMM.


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B. Check wiring continuity using a DMM.

1. Select the resistance function on the DMM and set to thelowest range.

2. Connect the red lead to the wire being tested and the blacklead to a good ground.

3. Check the reading. Compare to manufacturer’s specifications.A reading higher than specifications (usually greater than 1.0ohms) indicates an open in the circuit.

NOTE: Some DMMs are equipped with a setting formeasuring continuity and are designed to make a beepingsignal if the circuit is continuous.


5. Repair the circuit if an open is found.

C. If the reference voltage circuit connections are good and the circuitis continuous, perform an inspection of the electrical system thatsends current to the PCM.

II. Procedures for testing and servicing sensors

NOTE: These are general procedures. Follow manufacturer’srecommended procedures.

CAUTION: When connecting jumper wires, do not allow the wires totouch because this can burn out the sensors or PCM components.

A. Test and service the crankshaft position (CKP) sensor and otherpermanent magnet signal generators.

1. The CKP sensor is a permanent magnet signal generator thatdetermines rpm and cylinder position. The goal for testing isto determine if a proper voltage signal is produced.

2. Test the CKP sensor during engine cranking.

a. Select the alternating current (AC) voltage function onthe DMM and set to the proper range.

b. Disable the ignition system.


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c. Connect the jumper wires between the sensor terminalsand the PCM wiring terminal.

d. Connect the alligator clips to the probe ends.

e. Connect the black probe to the ground wire and the redprobe to the signal wire.

f. Crank the engine.

g. Check the reading. It should be constant AC voltage ofabout .8 volts to 3 volts. Compare to manufacturer’sspecifications.

h. Turn off the key. Enable the ignition system. Disconnectthe DMM.

3. Test the CKP sensor with the engine running.

a. Select the rpm/hertz (Hz) function on the DMM and setto the proper range.

b. With the key off/engine off, connect the jumper wiresbetween the sensor terminals and the PCM wiringterminal.

c. Connect the alligator clips to the probe ends.

d. Connect the black probe to the jumper running from theground wire and the red probe to the jumper runningfrom the signal wire.

e. Connect the exhaust ventilation equipment.


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CAUTION: Be sure to use approved exhaustventilation equipment when operating the vehicle inan enclosed area.

f. Start the engine.

g. Check the reading. Compare to manufacturer’sspecifications.

h. Shut off the engine. Disconnect the DMM and exhaustventilation equipment.

4. Perform a static resistance test on a CKP sensor.

a. Select the resistance function on the DMM and set to theproper range.

b. With the key off/engine off, disconnect the sensor wires.Connect both probes to the magnetic pickup.

c. Check the ohms reading. Compare to manufacturer’sspecifications.

d. Disconnect the DMM.

5. Test the CKP sensor using an oscilloscope.

a. Connect the oscilloscope according to manufacturer’sprocedures.


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b. Observe the pattern. Compare to a known goodpattern. The maximum peak levels should be equal. Ifone is shorter than the other, check for a chipped or benttooth on the trigger wheel.

c. Disconnect the oscilloscope.

6. Replace a malfunctioning CKP sensor. Use manufacturer’sprocedures. If the problem is caused by clearance between thereluctor and magnetic pickup coil, the clearance is adjustable.If the CKP sensor is adjustable, check clearance and adjustaccording to manufacturer’s specifications.

B. Test and service the Hall-effect sensor.

1. The Hall-effect sensor determines engine speed and cylinderpiston position. The goal for testing is to determine if voltage isproduced when a vane passes.

2. Test the Hall-effect sensor during engine cranking using aDMM with an analog bar graph or pointer.

a. Select the AC voltage function on the DMM and set tothe proper range.


c. Connect the jumper wires from the sensor terminals tothe wire leads for all the sensor wires.



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e. Connect the black probe to the jumper running from theground wire and the red probe to the jumper runningfrom the signal wire.


g. Check for bar graph pulses (usually between 0 volts and12 volts) as the vanes pass the sensor. Compare tomanufacturer’s specifications.

h. Turn off the key. Enable the ignition system. Disconnectthe DMM.

3. Test the Hall-effect sensor by passing a feeler gauge betweenthe magnet and semiconductor using a DMM with an analogbar graph or pointer.

a. Select the AC voltage function on the DMM and set tothe proper range.

b. With the key off/engine off, connect the jumper wiresfrom the sensor terminals to the wire leads for all thesensor wires.


d. Connect the black probe to the jumper running from theground wire and the red probe to the jumper runningfrom the signal wire.

e. With the key on/engine off, pass the feeler gaugebetween the magnet and the semiconductor.


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f. Check for bar graph pulses (usually between 0 volts and12 volts) as the feeler gauge passes between the magnetand semiconductor. Compare to manufacturer’sspecifications.

g. Turn the key off. Disconnect the DMM.

4. Test the Hall-effect sensor using a DMM with a duty cyclefunction.

a. Select the duty cycle function on the DMM and set to theproper range.


c. Connect the jumper wires from the sensor terminals to allthe sensor wires.


e. Connect the black probe to the jumper running from theground wire and the red probe to the jumper runningfrom the signal wire.



h. Shut off the engine. Enable the ignition system.Disconnect the DMM.

5. Test the Hall-effect sensor using an oscilloscope.


b. Observe the pattern. Compare to a known good pattern.

1. The upper horizontal lines should reach referencevoltage.


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2. The voltage transitions should be straight andvertical.

3. The peak-to-peak voltages should equal referencevoltage.

4. The lower horizontal lines should almost reachground.


6. Replace a malfunctioning Hall-effect sensor. Usemanufacturer’s procedures.

C. Test and service the engine coolant temperature (ECT) sensor.

1. The ECT sensor alters resistance in relation to the enginecoolant temperature. The goal for testing is to determine if theECT sensor properly alters resistance at various temperatures.

NOTE: Check mechanical problems before checking the ECTsensor. Check the engine coolant level and temperature.

2. Test the ECT sensor when the engine coolant is cold.

a. Select the ohmmeter function on the DMM and set to theproper range.

b. With the key off/engine off, determine engine coolanttemperature. It must be a relatively low temperature.

c. Disconnect the sensor wires.

d. Insert the DMM probes into the sensor leads.


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e. Check the reading. Resistance should be high. Compareto manufacturer’s specifications.

f. Disconnect the DMM. Reconnect the sensor wires.

3. Test the ECT sensor with the engine at normal operatingtemperature.


b. Disconnect the sensor wires.

c. Connect the exhaust ventilation equipment.


d. Start the engine and allow it to reach normal operatingtemperature.

e. Check the engine coolant temperature using athermometer.

f. Shut off the engine.

g. Insert the DMM probes into the sensor leads.

h. Check the reading. Resistance should drop as the enginewarms. Compare to manufacturer’s specifications.

i. Disconnect the DMM and exhaust ventilation equipment.Reconnect the sensor wires.

4. Test the ECT sensor using an oscilloscope.




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5. Replace a malfunctioning ECT sensor. Use manufacturer’sprocedures.

NOTE: Some service information requires coating the ECTsensor threads with a sealer before installation. Do notovertighten a new ECT sensor.

D. Test and service the intake air temperature (IAT) sensor.

1. The IAT sensor alters resistance in relation to the temperatureof air entering the intake manifold. The goal for testing is todetermine if the IAT sensor properly alters resistance inrelation to the temperature of air entering the intake manifold.

2. Test the IAT sensor with it at or near room temperature.



c. With the key off/engine off, insert the DMM probes intothe sensor leads.

d. Check the reading. Compare to manufacturer’sspecifications.

e. Disconnect the DMM. Reconnect the sensor wires.

3. Test the IAT sensor with the engine at normal operatingtemperature.



c. Connect the exhaust ventilation equipment.


d. Start the engine and allow it to reach normal operatingtemperature.


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e. Shut off the engine.

f. Check the reading. Compare to manufacturer’sspecifications.

g. Disconnect the DMM and exhaust ventilation equipment.

4. With the sensor removed from the vehicle, test the IAT sensor.


b. Insert the DMM probes into the sensor leads.

c. Heat the sensor with a hair dryer or similar device.

d. Check the reading. Compare to manufacturer’sspecifications.

e. Disconnect the DMM.

5. Test the IAT sensor using an oscilloscope. The procedure is thesame as the ECT sensor. See Section II.C.4.

6. Replace a malfunctioning IAT sensor. Use manufacturer’sprocedures.

E. Test and service the throttle position (TP) sensor.

1. The TP sensor varies resistance according to throttle position.The goal for testing is to determine if the TP sensor variesresistance according to throttle position.

NOTE: Check for mechanical problems before testing the TPsensor. Check for binding of the throttle shaft or linkages andfor proper seating. Check any other mechanical problemsrecommended by service information.

NOTE: A TP sensor affected by road shock can behavenormally during testing. Tap the TP sensor when moving thethrottle to simulate road shock.

2. Resistance test the TP sensor.



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c. With the key off/engine off, connect the DMM probes tothe sensor signal and ground terminals.

d. Slowly move the throttle from the open position to thewide open position.

e. Check the bar graph. It should move smoothly withoutskips. Compare to manufacturer’s specifications.

f. Disconnect the DMM. Reconnect the sensor wires.

3. Perform a voltage drop test on the TP sensor.

a. Select the voltage function on the DMM and set to theproper range.



d. Connect the black probe to a good, clean ground and thered probe to the jumper running from the signal wire.

e. With the key on/engine off, slowly move the throttlefrom the open position to the wide open position.

f. Check the bar graph. It should move smoothly withoutskips. Compare to manufacturer’s specifications.

g. Turn off the key. Disconnect the DMM.

4. Perform a voltage drop test on the TP sensor with the throttleat idle.





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d. Connect the black probe to a good, clean ground and thered probe to the jumper running from the signal wire.

e. Check that the throttle is at idle.

f. Turn the key on and engine off.


h. Turn off the key. Disconnect the DMM.

5. Test the TP using an oscilloscope.


b. Observe the pattern. Compare to a known good pattern.Voltage increase identifies enrichment. Peak voltageindicates wide open throttle. Voltage decrease identifiesthe throttle plate closing. Minimum voltage indicates aclosed throttle plate. DC offset indicates voltage at keyon with throttle plate closed.


6. Test the TP sensor using a scan tool.

a. Connect the scan tool to the data link connector (DLC).Set to monitor a TP sensor signal.

b. With the key on/engine off and without pushing on thethrottle pedal, check the idle throttle voltage. Compareto manufacturer’s specifications.

c. While checking the voltage signal, slowly push thethrottle pedal down. The voltage should increase and thevoltage change should follow pedal movement.


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d. With the throttle pedal held to the floor, check thewide open throttle voltage. Compare to manufacturer’sspecifications.

e. If the readings are not within specifications, the TPsensor may need to be adjusted. Not all TP sensors areadjustable.

f. Turn off the key. Disconnect the scan tool.

7. Adjust the TP sensor using a scan tool.

a. Connect the scan tool to the DLC. Set to monitor a TPsensor signal.

b. Loosen the mounting screws.

c. Observe the reading. Rotate the TP sensor until thereading is within specifications.

d. Torque the mounting screws. Check the reading again.Compare to manufacturer’s specifications.

e. Disconnect the scan tool.

8. Replace a malfunctioning TP sensor. Use manufacturer’sprocedures.

F. Test and service the manifold absolute pressure (MAP) sensor.

1. The MAP sensor alters reference voltage based on the manifoldabsolute pressure in the intake manifold. The goal for testing isto determine if the frequency or voltage signal sent to the PCMis altered properly according to manifold absolute pressure.

NOTE: If the vehicle has a separate barometric pressure(BARO) sensor, use the same testing procedures as the MAPsensor.

2. Test the MAP sensor for intermittent problems.

a. Select the DC voltage setting on the DMM and set to theproper range.

b. Connect the jumper wires from the sensor terminals tothe wire leads for all the sensor wires.


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d. Connect the black probe to the jumper running to theground wire and the red probe to the jumper runningfrom the signal wire.

e. With the key on/engine off, tap and heat (with a hairdryer or similar device) the sensor to induce intermittentproblems.

f. Check the reading. The voltage reading should be 5volts. Compare to manufacturer’s specifications.


3. Test the frequency-signal MAP sensor for proper operation.

a. Select the rpm/Hz function on the DMM and set to theproper range.




e. With the key on/engine off, draw a vacuum with a handvacuum pump.


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f. Check the Hz reading and analog bar graph. As greatervacuum is smoothly drawn, the reading should increasesmoothly and within specifications. Compare tomanufacturer’s specifications.


4. Test the frequency-signal MAP sensor using an oscilloscope.



1. Upper horizontal lines should reach referencevoltage.

2. Voltage transitions should be straight and vertical.

3. Peak-to-peak voltage should equal referencevoltage.

4. Lower horizontal lines should almost reach ground.

5. Voltage drop to ground should not exceed 400millivolts (mV). If voltage drop is greater than 400mV, check for a bad ground at the sensor or PCM.


5. Test the simple-voltage MAP sensor for proper operation.

a. Select the DC voltage setting on the DMM and set to theproper range.


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e. With the key on/engine off, draw a vacuum with a handvacuum pump.

f. Check the reading. As greater vacuum is smoothlydrawn, the reading should increase smoothly and withinspecifications. Compare to manufacturer’s specifications.


6. Test the simple-voltage MAP sensor using an oscilloscope.



1. High voltage indicates high intake manifoldpressure (low vacuum).

2. Low voltage indicates low intake manifold pressure(high vacuum).

3. As the throttle plate opens, intake manifoldpressure increases and vacuum decreases.


7. Replace a malfunctioning MAP sensor. Use manufacturer’sprocedures.


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G. Test and service the mass airflow (MAF) sensor.

1. The MAF sensor alters reference voltage based on the mass ofair entering the intake manifold. The goal for testing is todetermine if the frequency or voltage signal sent to the PCM isaltered properly according to mass airflow.

2. Test the frequency-signal MAF sensor for intermittentproblems.

a. Select the DC voltage function on the DMM and set tothe proper range.

NOTE: Even though the MAF sensor sends a frequencysignal, the signal is still read as constant voltage. Thefrequency signal is so high that it does not register on aregular DC voltage setting. A constant voltage reading ispreferred when checking for intermittent problemscaused by road shock or jarring.





f. Check the reading. It should be 2.5 volts. Compare tomanufacturer’s specifications.


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3. Test the frequency-signal MAF sensor for proper operation.

a. Select the rpm/Hz function on the DMM and set to theproper range.

b. Connect the exhaust ventilation equipment.




e. Connect the black probe to the jumper running to theground wire and the red probe to the jumper runningfrom the signal wire.


g. Smoothly vary the engine rpm. Check the reading andanalog bar graph. It should change smoothly withchanges in the engine rpm. Compare to manufacturer’sspecifications.


4. Test the frequency-signal MAF sensor using an oscilloscope.




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1. Upper horizontal lines should reach referencevoltage.

2. Peak-to-peak voltage should equal referencevoltage.

3. Lower horizontal lines should almost reach ground.


5. Test the simple-voltage MAF sensor for intermittent problems.

a. Select the DC voltage function on the DMM and set tothe proper range.




NOTE: A simple-voltage MAF sensor has an extra wire,the burn-off wire, that supplies current to burn off anycontamination of the wire element.


f. Check the reading. It should be 5 volts. Compare tomanufacturer’s specifications.



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6. Test the simple-voltage MAF sensor for proper operation.






e. Connect the black probe to the jumper running to theground wire and the red probe to the jumper runningfrom the signal wire.


g. Smoothly vary the engine rpm. Check the reading andanalog bar graph. It should change smoothly withchanges in rpm. Compare to manufacturer’sspecifications.


7. Test the simple-voltage MAF using an oscilloscope.





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8. Replace a malfunctioning MAF sensor. Use manufacturer’sprocedures.

H. Test and service the volume airflow (VAF) sensor.

1. The VAF sensor alters resistance according to the amount ofair entering the engine. The goal for testing is to determine ifthe VAF sensor varies resistance according to the amount ofair entering the engine.

2. Inspect the VAF.

a. Check the intake air duct leading to the VAF sensor fortears, holes, or deterioration that might allow debris toreach the VAF sensor.

b. Inspect the air filter and housing.

c. Inspect the electrical circuit for damaged or corrodedconnectors.

3. Test the VAF sensor by disconnecting the electrical connector.

a. Using a voltmeter, measure the reference voltage beingsent to the VAF sensor. Most systems use 5 volts.

b. Remove the air intake duct.

c. Connect an ohmmeter to the electrical connector.

d. While observing the reading, slowly move the flap insidethe VAF sensor. The reading should change smoothly. Ifthe reading is erratic, skips, or jumps, inspect the flap forbinding.

NOTE: The flap can bind because of dirt or greasebuildup. Remove buildup using carburetor cleaner.

e. Disconnect the ohmmeter.

4. Replace a malfunctioning VAF sensor. Use manufacturer’sprocedures.


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I. Test and service the oxygen sensor (O2S).

1. The O2S measures the amount of oxygen in the exhaust gasesbefore and after the catalytic converter. The goal for testing isto determine if the O2S properly alters resistance in relation tothe amount of oxygen in the exhaust gases.

2. Test the O2S using a DMM.

a. Connect one DMM lead to the output signal wire and theother to a good, clean ground.

CAUTION: Make the proper connections whentesting the O2S. A voltage surge can damage the O2Sand PCM.



c. Start the engine and allow it to reach normal operatingtemperature.

d. Check the voltage output.

e. Using propane enrichment equipment, create anartificially rich condition. Check the reading. It shouldbe higher than normal. Compare to manufacturer’sspecifications.

f. Using propane enrichment equipment, create anartificially lean condition by removing a vacuum line.Check the reading. It should be lower than normal.Compare to manufacturer’s specifications.

g. Shut off the engine. Disconnect the DMM and exhaustventilation equipment.

3. Test the O2S using an oscilloscope.



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1. Maximum peak voltage should be at least 800 mVor more.

2. Peak-to-peak voltage should be at least 600 mV ormore with an average of 450 mV.

3. Minimum peak voltage should be at least 200 mV orless.


4. Test the O2S using a scan tool.

a. Connect the scan tool to the DLC.



c. Start the engine and allow it to reach normal operatingtemperature.

d. Check the reading with the vehicle in closed loopoperation. An O2S located between the engine and thecatalytic converter should oscillate between 100 mV and900 mV. Compare to manufacturer’s specifications.

NOTE: Many vehicles are equipped with more than oneO2S. Check the correct sensor.

e. Shut off the engine. Disconnect the scan tool andexhaust ventilation equipment.

5. Replace a malfunctioning O2S. Use manufacturer’sprocedures.


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J. Test and service the knock sensor (KS).

1. The KS detects engine ping, preignition, or detonation. Thegoal for testing is to determine if the KS signals the PCM whenengine ping, preignition, or detonation occurs.

2. Test the KS using an oscilloscope.




3. Replace a malfunctioning KS. Use manufacturer’s procedures.

III. Procedures for testing and servicing the actuators

A. Test the solenoid.

1. Select the voltage function on the DMM and set to the properrange.

2. Connect the jumper wires to the battery and solenoid.

3. Check the reading. Compare to manufacturer’s specifications.If the solenoid is good, check the voltage to the solenoid fromits harness.



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5. Replace a malfunctioning solenoid. Use manufacturer’sprocedures.

B. Test relays. Because relays have moveable contact points, they are acommon source of problems.

1. Select the voltage function on the DMM and set to the properrange.

2. Check the voltage entering the relay and the voltage leavingthe relay. Compare to manufacturer’s specifications.


4. Replace malfunctioning relays. Use manufacturer’sprocedures.

C. Test the servo motor.

1. Connect an external voltage source.

2. Disconnect the wiring harness.

3. Connect the jumper wires. If the servo motor begins to work,it is good. If the servo motor is good, test the wiring harnessleading to the servo motor.

4. Disconnect the jumper wires. Reconnect the wiring harness.

5. Replace a malfunctioning servo motor. Use manufacturer’sprocedures.

D. Perform active tests of actuators using a bidirectional scan toolcapable of performing actuator tests.

1. Connect the scan tool to the DLC. Enter vehicle information.

2. From the display, select “Function Test” or “SpecialFunctions.”

NOTE: Most bidirectional scan tools will perform additionaltests, including power balance testing and communicationstesting, in the Function Test/Special Functions mode.

3. From the display, select “Actuator Test.”


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NOTE: Some scan tools may display a list of actuators byname, such as idle air controller.

4. Select the actuator to be tested and follow the scan toolinstructions for performing the test. Some tests will beperformed with the key on/engine off, and others will requirekey on/engine running.

5. Determine if the actuator responded correctly. If the actuatordid not respond correctly, determine necessary action. Includefurther diagnosis and/or repair(s).


7. Replace malfunctioning actuators. Use manufacturer’sprocedures.

IV. Procedures for testing and servicing computerized engine controls using agraphing multimeter (GMM) or digital storage oscilloscope (DSO)

NOTE: These are general procedures. Follow manufacturer’srecommended procedures.

A. Test the electrical/electronic circuits.

1. Configure the GMM/DSO for the electrical/electronic circuitsand connect the test leads.

2. Check the pattern. Compare to a known good pattern.

3. Disconnect the test leads.

B. Test the sensors.

1. Configure the GMM/DSO for the sensor to be tested andconnect the test leads.



C. Test the actuators.

1. Configure the GMM/DSO for the actuator and connect thetest leads.



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D. Test the PCM.

1. Configure the GMM/DSO for the PCM and connect the testleads.



E. Use manufacturer’s service information to repair problems foundduring testing.


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UNIT IV: DISTRIBUTOR IGNITION (DI) SYSTEMS


I. Unit objective

II. Lesson plans

A. Lesson 1: Overview and Theory of Distributor Ignition Systems


2. Assignment sheet

a. AS1-L1-UIV: Distributor Ignition Systems

B. Lesson 2: Diagnosing and Servicing Distributor Ignition Systems


2. Job Sheets

a. JS1-L2-UIV: Diagnose Ignition Sytems Problems on aVehicle with a Distributor Ignition System

b. JS2-L2-UIV: Inspect, Test, and Service the PrimaryCircuit and Ignition Coil

c. JS3-L2-UIV: Check and Adjust Ignition Timing andTiming Advance/Retard

d. JS4-L2-UIV: Inspect, Test, and Service the Distributor

e. JS5-L2-UIV: Inspect, Test, and Service Secondary CircuitWiring and Spark Plugs

III. Unit IV Test


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UNIT OBJECTIVE

After completing this unit, students should be able to diagnose and servicedistibutor ignition systems. Students will demonstrate mastery of the materialby completing the assignment sheet, successfully performing specific tasks onthe job sheets, and achieving a score of on the Unit IV Test.

SPECIFIC OBJECTIVES


Lesson 1

I. Identify terms and definitions associated with distributor ignition systems.

II. Describe the performance capabilities of distributor ignition systems.

III. Identify and describe the components of distributor ignition systems.

IV. Complete the assignment sheet on distributor ignition systems(AS1-L1-UIV).

Lesson 2

I. Explain the procedures for diagnosing ignition system problems on avehicle with a distributor ignition system.

II. Explain the procedures for inspecting and testing primary circuit wiring.

III. Explain the procedures for inspecting, testing, and replacing theignition coils.

IV. Explain the procedures for checking and adjusting ignition timing andtiming advance/retard.

V. Explain the procedures for inspecting, testing, and servicing thedistributor.

VI. Explain the procedures for inspecting, testing, and replacing thesecondary wiring.

VII. Explain the procedures for servicing spark plugs.


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VIII. Demonstrate the ability to:

A. Diagnose ignition system problems on a vehicle with a distributorignition system (JS1-L2-UIV).

B. Inspect, test, and service the primary circuit and ignition coil(JS2-L2-UIV).

C. Check and adjust ignition timing and timing advance/retard(JS3-L2-UIV).

D. Inspect, test, and service the distributor (JS4-L2-UIV).

E. Inspect, test, and service secondary circuit wiring and spark plugs(JS5-L2-UIV).


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LESSON 1: OVERVIEW AND THEORY OF DISTRIBUTOR IGNITIONSYSTEMS

I. Terms and definitions associated with distributor ignition (DI) systems

A. After top dead center (ATDC) — Piston position duringdownstroke.

B. Base timing — Ignition timing of an engine at idle speed and whenno advance mechanism is in operation.

C. Before top dead center (BTDC) — Piston position during upwardtravel.

D. Electromagnetic induction — Principle that states voltage isinduced in a conductor whenever the lines of force of a magneticfield cut across the conductor.

E. Firing order — Numerical order of spark plug firing.

F. Mutual inductance — Magnetic property whereby voltage isinduced in one coil because of a changing current in another coil.

G. Pre-ignition — Ignition of air/fuel mixture before the timed spark.

H. Reluctance — Naturally-occurring resistance to the buildup of amagnetic field.

I. Self-inductance — Magnetic property whereby voltage is inducedin a current-carrying wire when the current in the wire itself ischanging.

J. Top dead center (TDC) — Piston position at the top of travel.

II. Performance capabilities of DI systems

A. DI systems convert the 12 volts of electricity supplied by the batteryto at least 20,000 or more volts.

B. DI systems direct the high voltage to the proper spark plug at theproper time.

C. DI systems adjust the time that the voltage is directed to each sparkplug according to engine speed and load.


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III. Components of DI systems

NOTE: The components discussed in this section are basic componentsfound on all DI systems. Some older systems, such as breaker pointsystems, have additional components not discussed here.

A. The spark plug discharges a relatively high voltage (sometimes morethan 60,000 volts) inside the combustion chamber. This discharge isreferred to as firing the spark plug. When the spark plug fires, theair/fuel mixture is ignited.

1. Spark plugs have a steel shell with a ceramic insulator insertedinto the shell. Threads on the steel shell permit installation ofthe spark plug in the cylinder head.

2. The seal between the cylinder head and spark plug is done bya tapered seat machined into the steel shell with a matchingseat machined into the cylinder head. A special gasket canalso be used for the seal.


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3. Electrodes are the current-conducting electrical contacts of aspark plug. The center electrode travels through the center ofthe ceramic insulator. The side electrode is attached to thesteel shell.

NOTE: Electrodes can be constructed of a nickel chromiumalloy. Some designs incorporate platinum for a longer sparkplug life. Some manufacturers use bipolar ground electrodesto maintain spark plug durability.

4. The spark plug wires connect to a terminal that extends fromthe center electrode and out of the top of the insulator.

5. A carbon resistor is sometimes placed between the centerelectrode and terminal to suppress radio noise.

6. The ceramic insulator has ribs on the outer diameter to preventthe flashover of the high-voltage secondary from the sparkplug cable to the steel shell.

7. The optimum operating temperature of a spark plug isbetween 700°F to 1500°F.


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NOTE: A spark plug that operates at too high a temperaturemay begin to glow and become a source of pre-ignition. Aspark plug that operates at too low a temperature cannot burnoff the conductive deposits that develop from combustion andmisfires will occur.

8. Spark plug heat range is the ability of the spark plug todissipate heat from its firing end to the cylinder head andengine coolant. This is controlled by the length of the insulatorfiring tip.

a. A hot spark plug has a long firing tip because heat has agreater distance to travel as it is transferred from the tip,to the shell, cylinder head, and engine coolant.

b. A cold spark plug has a short firing tip that allows forfaster heat transfer.

9. Spark plug reach is the length of the steel shell from the pointat which it contacts the cylinder head to the bottom of the steelshell. It includes both the threaded and non-threaded sections.

NOTE: A spark plug should never be interchanged with onethat has a different reach. Poor engine performance or enginedamage can result.

B. Spark plug wires are radio-suppression wires designed to preventhigh-frequency radio interference emitted by copper or other typesof spark plug wires.


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1. Spark plug wires are made of a fiberglass or aramid fiber stringtransfused with carbon.

2. Insulating rubber covers the carbon string and a protectiveouter jacket of neoprene or silicone is installed. Copper orstainless steel terminals are connected to each end and aremade to snap on the spark plugs and distributor cap. Bootsmade of heavy rubber insulate the terminals.

C. The distributor directs electrical current to each spark plug at theproper firing time.

1. In each cylinder, the spark plug must fire when the piston is inthe compression stroke, so all spark plugs cannot fire at once.

2. Electrical current must be delivered to each spark plug at thetime the cylinder is supposed to fire.

D. The distributor cap attaches to the top portion of the distributorwith screws or spring clips. It is made of either bakelite or a specialinsulating plastic.

1. A coil wire tower extends from the center of the distributorcap. A carbon insert on the inside of the tower carries the highvoltage from the ignition coil to the rotor.


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2. Spark plug towers extend from the top of the distributor caparound the outer circumference. Copper or aluminumcontacts are molded into each of the towers. Spark plug cablesconnect to each of the towers.

3. In addition to directing high voltage from the coil secondary tothe proper spark plug, the distributor cap also seals thedistributor housing from dirt and moisture.

4. Larger distributor caps with terminals spaced farther apart aresometimes used to protect against arc-over betweenterminals because of available higher voltage.

E. The rotor rotates with the distributor shaft. It is mounted on theupper end of the distributor shaft under the distributor cap and isheld in place by a press fit or with screws.

1. Rotors are made of bakelite or a special insulating plastic witha spring steel contact, which rests against the carbon button inthe distributor cap.

2. As the distributor shaft rotates, a copper contact attached tothe rotor delivers high voltage from the spring steel contact tothe proper spark plug wire terminal on the distributor cap.

3. A small air gap is provided between the tip and the distributorcap secondary tower. The high-voltage electrical current mustcross this air gap as it travels to the spark plug.

4. Larger rotors and special insulating plastics are sometimesused to prevent arc-over of high-voltage electricity.

F. The ignition coil produces the high voltage necessary to create thespark.

1. The two types of ignition coils are type A and type B. Theinternal wiring is physically different in these two types.


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a. In a type A coil, the primary circuit is wired from theprimary positive terminal to the primary negativeterminal. The secondary circuit is wired from theprimary positive terminal to the secondary terminal.

b. In a type B coil, the primary circuit is wired from theprimary positive terminal to the primary negativeterminal. The secondary circuit is wired from the groundto the secondary terminal.


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G. Computerized systems use the powertrain control module (PCM) tocontrol the ignition process and to establish ignition timing usinginput from various sensors.


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LESSON 2: DIAGNOSING AND SERVICING DISTRIBUTOR IGNITIONSYSTEMS

NOTE: The procedures in this lesson are general procedures. Check serviceinformation before beginning procedures. Follow manufacturer’srecommended procedures.

I. Procedures for diagnosing ignition system problems on a vehicle with adistributor ignition (DI) system

A. Identify ignition system concerns. Check for no-start, hard start,misfire, poor driveability, spark knock, power loss, poor mileage,and emissions concerns.

B. Depending on the concerns, test the possible causes of the concernsusing available service information.

C. Using a scan tool, check and record diagnostic trouble codes(DTCs), snapshot information, and datastream information relatedto the concerns.

D. If there is a no-start condition, test the components and systemsusing a digital multimeter (DMM). Make sure to test the following.

• Crankshaft position (CKP) sensor• Camshaft position (CMP) sensor• Distributor shaft position sensor• Ignition control module• Ignition coils• Powertrain control module (PCM)• Primary circuit wiring and voltage• Secondary circuit wiring and voltage• Distributor caps• Rotor

E. Perform an exhaust gas diagnostic test.




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5. Check the exhaust gas analyzer readings. Compare readingsto proper specifications.


F. Based on the tests, determine necessary action to correct anyproblems. Include further diagnosis and/or repairs.

II. Procedures for inspecting and testing primary circuit wiring

A. Inspect the primary circuit wiring.

1. Inspect wiring for worn or cracked insulation. Repair orreplace as necessary.

2. Check for loose or broken wire terminals. Repair as necessary.

3. Check routing of the primary wiring. Reroute wiring that istouching the exhaust manifold or other hot surfaces.

B. Test the primary circuit.

CAUTION: It may be necessary to connect the exhaustventilation equipment during testing.

1. Check voltage drop across the resistor bypass circuit whilecranking the engine.

a. Remove the coil secondary wire at the distributor andground it.


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b. Connect the DMM.

c. Crank the engine. The reading should be less than 1 volt.Turn off the ignition switch.

d. A reading over 1 volt indicates the following.

• Open circuit between battery and battery side ofignition coil

• Failure of ignition switch to close• Ground in resistor bypass circuit• Ground in ignition coil


2. Measure available voltage at the side of the ignition coil.

a. Connect the DMM.

b. Turn the ignition switch to the run position. The readingshould show normal battery voltage. Turn off theignition switch.


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c. A reading of less than battery voltage indicates thefollowing.

• Battery with a low state of charge• Shorted ignition module control circuit• Ground in circuit between ignition coil and

distributor• Ground in circuit used during cranking or in

resistance lead or lead connecting ignition coil toresistor


3. Check voltage drop across the coil primary.

a. Connect the DMM.

b. Turn the ignition switch to the run position. The readingshould be between 5.5 and 7.5 volts. Turn off the ignitionswitch.

c. A reading over 7.5 volts indicates the following.

• Open ignition module control circuit• Loose connection in distributor circuitry• High resistance between distributor contacts• Loose connection between ignition coil and

distributor• Shorted-out resistor between ignition switch and

ignition coil• Ignition switch remains closed while in cranking

position• Open coil primary winding• No ground from distributor to engine


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d. A reading under 5.5 volts indicates the following.

• Loose connection between resistor and ignition coil• Open resistor• Loose connection between battery and resistor


4. Check voltage drop across the primary control circuit.

a. Connect the DMM.

b. Turn the ignition switch to the run position whilecranking the engine or with the engine running. Thereading should not exceed 0.2 volts. Turn off the ignitionswitch.

c. A reading that exceeds 0.2 volts indicates the following.

• Open in ignition module control circuit• Loose connection in distributor circuitry• Poor or no ground from distributor to engine• High resistance between distributor contacts


5. Check voltage drop across the circuit between the ignitionswitch and resistor.

NOTE: Not all solid-state systems use a resistor between theignition switch and coil primary, so it may be necessary tomeasure available battery voltage.

NOTE: Most engines must be cranked to do this test.


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a. Connect the DMM.

b. Turn the ignition switch to the run position. The readingshould range between 4.5 and 6.6 volts. Turn off theignition switch.

c. A reading less than 4.5 volts or more than 6.6 voltsindicates a damaged resistor.


III. Procedures for inspecting, testing, and replacing the ignition coils

A. Inspect the ignition coils.

NOTE: Ignition coils do not require periodic service. An inspectionis recommended when other ignition work is performed.

NOTE: Before performing an inspection, it may be necessary toclean the ignition coil with an electrical parts cleaner.

1. Inspect the ignition coil cover for cracks or carbon tracking,traces of carbon found in the ignition coil, distributor cap, orrotor that leads away some electricity.

2. Inspect the primary wiring. Repair or replace as necessary.

3. Inspect the secondary coil wire. Repair or replace asnecessary.

4. Check the tightness of the wiring connections. The secondarywire should be pressed all the way into its socket and theinsulating boot should be in place. Tighten as necessary.


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5. Remove the secondary wire from the coil tower. Inspect thewire and coil tower. Replace if the coil tower is eroded due topoor wiring connection.

NOTE: Corrosion in the coil tower may be cleaned with asmall wire brush.

6. Check the coil polarity.

a. The coil primary terminals are normally marked positive(+) and negative (-).

b. In a negative ground system, the (-) terminal should beconnected to the distributor primary lead.

c. In a positive ground system, the (+) terminal should beconnected to the distributor primary lead.

NOTE: On solid-state systems, coil polarity is oftendifficult to detect. If coil polarity is thought to beincorrect, consult service information for proper wiringconnections at the coil primary.

B. Test the ignition coil.

1. Identify the type of ignition coil. Epoxy-filled coils can beidentified by examining the wiring.

a. Type A coils are installed in the traditional metal can andhave three terminals: primary positive, primary negative,and high-voltage output.

b. Type B coils have four terminals: primary positive,primary negative, high-voltage output, and ground.

2. Test the primary resistance of the ignition coil.

a. Turn off the ignition switch.

b. Disconnect the primary and secondary coil terminals.

c. Connect the DMM leads to the primary positive (+) andnegative (-) terminals.

d. Read the resistance. Compare reading to manufacturer'sspecifications. Replace as necessary.


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3. Test the secondary resistance of the ignition coil.

a. Connect the DMM leads from the primary positive (+)terminal to the secondary coil terminal.

b. Read the resistance. Compare reading to manufacturer'sspecifications. Replace as necessary.

c. Disconnect the DMM.

C. Replace the ignition coil.

NOTE: Manufacturers recommend replacing the ignition coilinstead of attempting to repair it.

1. Disconnect the primary leads from the ignition coil. Note theposition of the wires for proper reassembly.

2. Disconnect the secondary coil wire.

3. Loosen the coil mounting bracket and remove the ignition coil.

4. Reverse the steps for installation.

IV. Procedures for checking and adjusting ignition timing and timingadvance/retard

A. Ignition timing must be accurate for optimum performance. Timingadvance is a change of timing so that ignition occurs earlier in thecycle. Timing retard is a change of timing so that ignition occurslater in the cycle.

B. There are two different types of timing equipment.

1. The timing light is the most common device. It is a strobe lightthat is triggered by the firing of the Number 1 spark plug. Thetiming light flashes every time the Number 1 spark plug fires.

a. The flashing beam is pointed at the timing marks on theengine. The timing is then adjusted until the flash occurswhen the appropriate timing mark passes the pointer orindicator mark.

b. Timing marks are located on the harmonic balancer witha pointer on the front engine cover.


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1. Some engines have a timing tab attached to thefront engine cover. Timing marks are found on thetab. A notch or line on the crankshaft pulley orharmonic balancer corresponds to the timing tab.

2. Other engines have timing marks on the engineflywheel. These correspond to marks or a pointeron the engine block.

2. The timing meter is used in crowded engine compartmentsand provides a more accurate measure of ignition timing.

NOTE: Only engines with provisions for locating the triggerof the timing meter can be timed with a timing meter.

a. The trigger device is a magnetic probe from the timingmeter. It is inserted into a socket at the harmonicbalancer. The probe senses the passing of a strategically-placed slot in the harmonic balancer every time thecrankshaft rotates.

b. The magnetic field of the probe is interrupted when theslot in the harmonic balancer passes the probe. Theprobe senses this break and transmits a signal to thetiming meter, which interprets and registers the signal indegrees of crankshaft rotation.

C. Time an engine using a timing light.

1. Use service information to obtain timing specifications.

a. The specifications normally are given for a certain enginerpm, such as 6° before top dead center (TDC) at 600 rpm.

b. The rpms are critical during a timing check. If the idlespeed is too fast, the centrifugal advance unit may be inoperation, which gives a false reading.

NOTE: Other specific instructions are usually includedin addition to timing specifications. Timing informationis usually found on the emissions decal. Readinstructions carefully before checking and adjustingtiming.

2. Clean timing marks thoroughly to increase visibility. It isusually helpful to place a chalk mark on the specified timingmark.


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NOTE: Correction fluid or touch-up paint can be used tomake the specified timing mark.

3. Connect a tachometer and timing light to the engine.Disconnect vacuum advance and other devices as directed bythe emissions decal.



5. Start the engine and set the idle speed to specification.

6. Direct the timing light at the timing marks and read timing.

a. If timing is incorrect, loosen the distributor hold-downbolt. Turn the distributor to either advance or retarduntil desired timing is achieved.

b. Tighten the distributor hold-down bolt and rechecktiming. Readjust if necessary.

7. Test the centrifugal advance unit.

a. With the timing light in position, increase the enginespeed to 2000 rpm. Note whether the timing advancesand if the maximum amount of advance is achieved.Compare to manufacturer's specifications.

b. If timing advances smoothly, the unit is functioningnormally.

c. If timing does not advance or is jerky, the unit is notworking or is sticking. Clean or repair as necessary.

8. Test the vacuum advance unit.

a. With the engine at idle, disconnect the advance hose tothe vacuum advance unit.

b. Connect a vacuum pressure pump to the vacuumadvance unit.

c. Direct the timing light on the timing indicator and apply15 inches of vacuum to the vacuum advance unit.


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d. The timing should advance smoothly. Note themaximum amount of advance. Compare tomanufacturer's specifications.

e. If timing advances smoothly, the vacuum advance isfunctioning normally.

f. If there is no vacuum advance, the vacuum diaphragmmay be leaking or the breaker plate may be sticking.

9. Shut off the engine. Disconnect the tachometer and timinglight. Disconnect the vacuum pressure pump. Disconnect theexhaust ventilation equipment.

D. Check and adjust ignition timing and timing advance/retard usinga timing meter.

1. Use service information to obtain timing specifications.

2. Insert the magnetic probe of the timing meter in the probereceptacle until the probe tip contacts the harmonic balancer.

CAUTION: Do not insert the probe with the engine on.The probe must be clear of the fan, pulleys, etc.

NOTE: An adapter is required to fit the probe to somevehicles. Consult service information for the properprocedure.

3. Power up the timing meter as directed by the manufacturer.



5. Start the engine. Prepare the engine as directed by themanufacturer.


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6. Read ignition timing on the timing meter.

7. Test the centrifugal and vacuum advance units as described insections IV.C.7 and IV.C.8. Refer to manufacturer'sspecifications for the amount of centrifugal and vacuumadvance and total timing advance.

8. Shut off the engine. Disconnect the timing probe and adapter.Disconnect the vacuum pressure pump. Disconnect theexhaust ventilation equipment.

V. Procedures for inspecting, testing, and servicing the distributor

A. Perform a visual inspection of the distributor assembly.

B. Inspect and test the distributor electronic components usingavailable service information. The procedure should be appropriatefor the specific distributor.

C. If applicable, inspect and test the distributor advance component.

D. Inspect the distributor cap.

1. Inspect the distributor cap for cracks or carbon tracking.Replace as necessary.

2. Inspect the cap for badly burned contacts. Moderate burningis normal. Replace as necessary.

NOTE: Some manufacturers use a silicone dielectriccompound on the distributor to suppress radio noise that takeson a charred look with age. This is normal and does not affectperformance. Do not remove the compound.

3. Check for corrosion in the coil towers. Remove corrosion witha small wire brush. Replace as necessary.


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4. Check wires for tight connections in the coil towers. Looseconnections cause arcing and burning that erodes the cap.

5. Using a DMM, measure the resistance of the contacts to thecoil towers. Compare to manufacturer’s specifications.

E. Inspect and test the rotor.

1. Check the rotor for cracks or carbon tracking. Replace asnecessary.

2. Inspect for signs of "burn-through," holes burned in the rotordue to high-voltage arcing. Replace as necessary.

3. Examine the rotor tip for signs of excessive burning. Replaceas necessary.

NOTE: Some manufacturers use a silicone dielectriccompound on the rotor tips that takes on a charred look withage. This is normal and does not affect performance. Do notremove the compound. When installing a new rotor, apply athin coat of compound (1/32” thick) to the tip.

4. Check the rotor spring contact for adequate tension and wearat the distributor cap carbon button contact area. Replace asnecessary.

5. Using a DMM, measure resistance. Compare tomanufacturer’s specifications.

F. Remove the distributor.

1. Clean debris from around the base of the distributor housing.

2. If equipped, disconnect the vacuum advance hose.


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3. Disconnect the primary wiring.

4. Remove the distributor cap.

NOTE: If removing spark plug wires, mark their position forproper reassembly.

5. Crank the engine until the rotor is in position to fire theNumber 1 cylinder and the timing mark is aligned with theTDC mark.

NOTE: If timing marks are not visible, mark the distributorhousing at the point at which the rotor is pointing. Then makeanother mark on the distributor housing and a correspondingmark on the engine block. These marks help during thereassembly process.

6. Remove the distributor hold-down clamp.

7. Remove the distributor.

8. Place a clean towel over the hole in the engine where thedistributor was removed.

G. Service the distributor.

1. Disassemble the distributor using available service information.The procedure should be appropriate for the specificdistributor.

a. Remove the rotor.

b. Remove the permanent magnet signal generator or Hall-effect sensor.

c. Remove the vacuum advance unit.

d. If applicable, remove the ignition module.

e. Remove the centrifugal advance springs and weights.

f. Support the distributor and drive out the roll pinretaining the distributor gear to the shaft. Slide thedistributor gear off the shaft.

g. Remove the distributor shaft.


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h. Separate the upper and lower shafts.

i. If applicable, remove the primary wiring lead.

2. Using safety solvent, clean the distributor housing, distributorshaft, and centrifugal advance components. Blow dry.

NOTE: Do not clean the vacuum advance, ignition module,and Hall-effect sensor or permanent magnet signal generatorin safety solvent. Wipe these clean with a shop towel.

3. Inspect the distributor shaft and bushing for wear.

4. Inspect the drive gear for scoring or excessive wear.

5. Repair or replace defective or worn components including thedistributor advance component, distributor cap, and rotor.

a. Repair or replace the distributor advance componentusing available service information. The procedureshould be appropriate for the specific distributor.

b. Replace the distributor cap.

NOTE: Improper installation of the distributor cap canlead to a damaged or broken distributor cap and rotorwhen the engine is cranked.

1. Loosen the hold-down screws or release the hold-down clips.

2. Raise the distributor cap up and clear of the rotor.

3. If required, apply a light film of silicone dielectriccompound to the distributor contacts.

4. Hold the new distributor cap beside the old onewith the alignment tab or other positioning mark inthe same position.

5. Remove the wires from the old distributor cap andinsert firmly into the new one.

6. Install each wire in the proper tower thatcorresponds to the tower in the old distributor cap.


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7. Seat the cap on the distributor housing. Make surethe alignment tab is in the proper position and thedistributor cap is installed squarely.

c. Replace the rotor.

1. Remove the distributor cap.

2. Remove the rotor from the distributor shaft. Rotorsare normally removed by taking away the twoattaching screws or pulling the rotor straight upand off the distributor shaft.

3. Install the new rotor.

4. Align the tabs on the rotor with the notch in thedistributor shaft and press onto the shaft or securewith mounting screws.

5. If mounting screws are used to retain the rotor,tighten the screws securely. Do not overtighten thescrews because it is possible to crack the rotor.

6. If required, apply silicone dielectric compound tothe rotor tip.

7. Reinstall the distributor cap.

6. Replace defective electronic components using available serviceinformation. The procedure should be appropriate for thespecific distributor.

7. Reassemble and lubricate the distributor using available serviceinformation. The procedure should be appropriate for thespecific distributor.

a. Install the parts in reverse order of disassembly.

b. Lubricate the distributor shaft and bushings.

c. If applicable, apply cam lubricant to the distributor cam.

d. If applicable, apply silicone grease to the ignition modulebase.

e. If a distributor tester is available, test the operation of thedistributor and vacuum advance unit.


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H. Install the distributor.

1. Remove the towel and place the distributor in the engine.Align the marks made during removal.

NOTE: Do not force the distributor into the engine. It may benecessary to use a long screwdriver to turn the oil pump toalign the drive coupling before inserting the distributor.

2. Install the distributor hold-down clamp and bolt. Snug, but donot tighten, the hold-down bolt.

3. Install the distributor cap, vacuum advance line, and primarywiring.



5. Start the engine and set timing to specifications. (See sectionIV. for timing procedures.)

6. Shut off the engine and disconnect the exhaust ventilationequipment.

VI. Procedures for inspecting, testing, and replacing the secondary wiring

A. Inspect the secondary wiring.

1. Inspect the wiring insulation for cracking, chafing, oil soaking,or other damage. Replace as necessary.

2. Inspect the wire boots for splitting, tears, or missing boots.Replace as necessary.

3. Check for loose wiring at the spark plugs, distributor cap, andignition coil. Tighten loose-fitting spark plug end terminals bysqueezing the terminal lightly with pliers. Be careful not todamage wire boots.


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4. Inspect the routing of the spark plug wires.

a. To prevent crossfire, check that spark plug wires areseparate if connected to cylinders that fire consecutively.

b. Crossfire results from induction of voltage in a spark plugwire from the magnetic field surrounding a nearby sparkplug wire. It most commonly occurs when two sparkplug wires that fire adjacent cylinders in the firing orderare routed side-by-side.

5. Check that wires are in their retaining/mounting clips androuted in the original pattern.

B. Test the resistance of the spark plug wires.

1. Connect one DMM lead to each end of the spark plug wire.

2. Check the reading. Compare to manufacturer’s specifications.A typical maximum resistance is 7,000 ohms per foot. Replaceas necessary.

NOTE: Specifications vary greatly. Check manufacturer'sspecifications before passing or condemning a wire.


C. Replace spark plug wires.

1. Grasp the wire by the wire boot and remove by gently twistingand pulling.

NOTE: Do not remove the spark plug wires by pulling hardon the wire because this can break the carbon string.

2. Note the routing of each wire and reinstall the retaining clips.

3. Install the wires by pushing the wires firmly onto the sparkplug terminals and distributor cap towers.

4. If the wire boot is the only item that must be replaced,carefully cut the old boot from the wire. Lubricate the newboot with spray silicone lubricant and slide the boot onto thewire. Do not pull on the wire.


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VII. Procedures for servicing spark plugs

A. Remove the spark plugs.

CAUTION: It is important to follow the proper procedures whenremoving and installing spark plugs. It is also important to befamiliar with procedures for inspecting spark plugs whenremoved from the engine.

1. Grasp the spark plug wire by the wire boot and remove bygently twisting and pulling. Remove all spark plug wires. Ifnecessary, label the wires with tape to ensure properreinstallation.

2. Use compressed air to blow dirt or other contaminants fromaround each spark plug.

3. Select the proper spark plug socket, a deep-well socket with aspecial rubber insert that protects the porcelain insulator.

4. Remove each spark plug. If any of the spark plugs areexcessively tight, apply a penetrating lubricant to the base ofthe spark plug.

NOTE: Keep the spark plugs in order so that any problemsfound can be traced to the proper cylinder.

B. Inspect the spark plugs.

1. Inspect the condition of the electrodes. Replace as necessary.

2. Inspect the electrode gap. The gap should be set tomanufacturer's specifications.

3. Inspect the spark plugs for fouling. Spark plugs should beclean with no foreign deposits on the insulator or shell.Replace as necessary.

4. Inspect the insulator. Replace as necessary.

5. Examine each spark plug for any conditions that mightshorten the life of the spark plug or indicate engine problems.


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C. Install the spark plugs.

1. Adjust the electrode gap of each spark plug to specification.Use a spark plug gap gauge to bend the side electrode to adjustthe spark plug gap.

NOTE: Bend only the side electrode. Bending the centerelectrode breaks the insulator and destroys the spark plug.

2. If the spark plugs are the gasket-seat type, check that thegasket is in place.

NOTE: If the spark plugs seemed overly tight when removed,there is most likely excessive carbon buildup on the thread areaof the spark plug and cylinder head. Use a thread chaser toremove carbon buildup.

3. Install the spark plugs finger tight in the cylinder head.

NOTE: When working with an aluminum cylinder head,apply a conductive-type antiseize compound to the threadsbefore installation to prevent sticking or seizing and help withfuture removal of the spark plugs.

4. Tighten spark plugs to specified torque with a spark plugsocket and torque wrench.


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UNIT V: ELECTRONIC IGNITION (EI) SYSTEMS


I. Unit objective

II. Lesson plans

A. Lesson 1: Overview and Theory of Electronic Ignition Systems


2. Assignment sheet

a. AS1-L1-UV: Electronic Ignition Systems

B. Lesson 2: Diagnosing and Servicing Electronic Ignition Systems


2. Job sheets

a. JS1-L2-UV: Diagnose Ignition System Problems on aVehicle with an Electronic Ignition System

b. JS2-L2-UV: Inspect, Test, and Service the Primary Circuitand Ignition Coils

c. JS3-L2-UV: Inspect, Test, and Service Secondary CircuitWiring and Spark Plugs

III. Unit V Test


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UNIT OBJECTIVE

After completing this unit, students should be able to diagnose and serviceelectronic ignition systems. Students will demonstrate mastery of the materialby completing the assignment sheet, successfully performing specific tasks onthe job sheets, and achieving a score of on the Unit V Test.

SPECIFIC OBJECTIVES


Lesson 1

I. Explain the basic operation of electronic ignition systems.

II. Identify and describe the components of electronic ignition systems.

III. Explain the basics of wasted-spark systems.

IV. Explain the basics of unit ignition systems.

V. Explain the advantages of electronic ignition systems.

VI. Complete the assignment sheet on electronic ignition systems(AS1-L1-UV).

Lesson 2

I. Explain the procedures for diagnosing ignition system problems on avehicle with an electronic ignition system.

II. Explain the procedures for inspecting and testing the primary circuitwiring.

III. Explain the procedures for inspecting, testing, and replacing the ignitioncoils.

IV. Explain the procedures for checking and adjusting ignition timing andtiming advance/retard.

V. Explain the procedures for inspecting, testing, and replacing thesecondary wiring.


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VI. Explain the procedures for servicing the spark plugs.

VII. Demonstrate the ability to:

A. Diagnose ignition system problems on a vehicle with an electronicignition system (JS1-L2-UV).

B. Inspect, test, and service the primary circuit and ignition coils(JS2-L2-UV).

C. Inspect, test, and service secondary circuit wiring and spark plugs(JS3-L2-UV).


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LESSON 1: OVERVIEW AND THEORY OF ELECTRONIC IGNITIONSYSTEMS

I. Basic operation of electronic ignition (EI) systems

A. EI systems were once referred to as distributorless ignition systems,or DIS, because these systems do not use a distributor.

1. These systems use one ignition coil for every two cylinders(wasted-spark) or one ignition coil for each cylinder (unitignition).

2. The powertrain control module (PCM) sends a signal based oninput from various sensors to the electronic coil module to firethe first ignition coil at the proper time.

3. The ignition coil secondary output then fires the spark plugs.

4. When the next trigger wheel tooth aligns with the crankshaftposition (CKP) sensor, the next ignition coil fires.

5. This process is repeated as the engine runs.

II. Components of EI systems

A. The spark plug discharges a relatively high voltage (sometimes morethan 60,000 volts) inside the combustion chamber. This discharge isreferred to as firing the spark plug. When the spark plug fires, theair/fuel mixture is ignited.


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NOTE: For more information on spark plugs, see Unit IV -Distributor Ignition (DI) Systems, Lesson 1, section III.A.

B. Spark plug wires are radio-suppression wires designed to preventhigh-frequency radio interference emitted by copper or other typesof spark plug wires.

NOTE: For more information on spark plug wires, see Unit IV -Distributor Ignition (DI) Systems, Lesson 1, section III.B.

C. The electronic coil module consists of several ignition coils and anelectronic circuit for operating the ignition coils. The electroniccircuit replaces the ignition control module in DI systems. It is morecomplex because it must analyze data from the PCM and sensors.

D. An EI system uses sensors as triggering devices.

1. The camshaft position (CMP) sensor is installed in place of thedistributor. It sends signals to the PCM on camshaft and valveposition.

2. The crankshaft position (CKP) sensor sends signals to the PCMon engine speed and piston position.

3. The knock sensor (KS) can be used to allow the EI system toretard timing if the engine knocks, or pings.

E. The PCM monitors the sensors and sends a signal to the electroniccoil module to fire the ignition coils at the proper time.


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III. Basics of wasted-spark systems

A. A wasted-spark system uses one ignition coil for every twocylinders. Each ignition coil serves two cylinders opposite eachother in the firing sequence. When the ignition coil fires, a spark issimultaneously delivered to both cylinders.

1. The ignition coil delivers the spark to one cylinder when itspiston is in the power stroke.

2. The ignition coil delivers the spark to the other cylinder whenits piston is in the exhaust stroke.

3. The spark that goes to the cylinder when its piston is in itsexhaust stroke is wasted.

B. One spark plug always fires in the normal direction of current flowwhile the other one fires backwards.

1. In distributor ignition systems, the secondary current normallyflows from the center electrode to the side electrode of thespark plug and then returns through the engine block.Electrons more readily leave the hotter center electrode andtravel to the cooler side electrode.

2. If current flow is reversed, it takes a higher ignition coil outputvoltage to fire the spark plug. If current flows from the colderside electrode to the hotter center electrode, approximately30% more voltage is required to fire the spark plug.

3. Conventional ignition systems did not function well withbackwards current flow because of the inability to produce theadditional voltage required to fire the spark plugs.

4. The wasted-spark system fires the spark plugs with reversecurrent flow without problems because of greater ignition coilprimary current.

IV. Basics of unit ignition systems

A. A unit ignition system, or direct ignition system, uses one ignitioncoil for each cylinder.


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1. In some systems, the ignition coil is mounted directly to thespark plug.

2. In other systems, the ignition coil is mounted near the sparkplug and connects with short secondary ignition cables.

V. Advantages of EI systems

A. EI systems have fewer moving parts, and there is no mechanicaldistributor to wear or break. This results in less maintenance andbreakdowns.


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B. EI systems use less space and fit well in crowded enginecompartments. Also, the ignition coils and PCM can be mountedremotely.

C. There is reduced load on the engine because the engine does notmove a distributor shaft.

D. EI systems have no mechanical timing adjustment because thetiming is predetermined and preset.

E. Dwell time is increased. The ignition coil "on" time is increasedbecause there is more than one ignition coil. This allows currentflow in the coil primary to increase to a higher level, resulting inhigher secondary voltage.

F. EI systems provide for longer ignition coil cooldown. Each ignitioncoil does not have to work as hard because there is more than oneignition coil, resulting in longer ignition coil life.


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LESSON 2: DIAGNOSING AND SERVICING ELECTRONIC IGNITIONSYSTEMS

NOTE: The procedures in this lesson are general procedures. Check serviceinformation before beginning procedures. Follow manufacturer’srecommended procedures.

I. Procedures for diagnosing ignition system problems on a vehicle with anelectronic ignition (EI) system

A. Identify ignition system concerns. Check for no-start, hard start,misfire, poor driveability, spark knock, power loss, poor mileage,and emissions concerns.

B. Depending on the concerns, test the possible causes of the concernsusing available service information.

C. Using a scan tool, check and record diagnostic trouble codes(DTCs), snapshot information, and datastream information relatedto the concerns.

D. If there is a no-start condition, test the components and systemsusing a digital multimeter (DMM). Make sure to test the following:

• Camshaft position (CMP) sensor• Crankshaft position (CKP) sensor• Knock sensor (KS)• Electronic coil module• Ignition coils• Powertrain control module (PCM)• Primary circuit wiring and voltage• Secondary circuit wiring and voltage

E. Perform an exhaust gas diagnostic test.





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5. Check the exhaust gas analyzer readings. Compare reading toproper specifications.


F. Based on the tests, determine necessary action to correct anyproblems. Include further diagnosis and/or repairs.

II. Procedures for inspecting and testing the primary circuit wiring

A. Using a scan tool, check and record DTCs, snapshot information,and datastream information for readings.

B. Inspect the primary circuit wiring.

1. Inspect the wiring for worn or cracked insulation. Repair orreplace as necessary.

2. Check for loose or broken wire terminals. Repair as necessary.

3. Check routing of the primary wiring. Reroute wiring that istouching the exhaust manifold or other hot surfaces.

C. Test the primary circuit using a digital multimeter (DMM).

NOTE: Because there are few or no moving parts, testing isprimarily limited to checking continuity and voltage testing ofprimary circuit wiring. This includes wiring to and from the PCM.

1. Check for proper battery voltage. Improper battery voltageinterferes with the ignition system and other electronic enginecontrols.

2. Test the continuity of the resistor circuit.

3. Test the wiring to and from the PCM.

III. Procedures for inspecting, testing, and replacing the ignition coils

NOTE: Ignition coils do not require periodic service. An inspection isrecommended when other ignition work is performed.


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NOTE: Before performing an inspection, it may be necessary to clean theignition coil with an electrical parts cleaner.

A. Inspect the electronic coil module and ignition coils.

1. Inspect the electronic coil cover for cracks or carbon tracking,traces of carbon found in the ignition coils that lead awaysome electricity. Replace as necessary.

2. Inspect the electronic coil module for damage. Replace asnecessary.

3. Inspect the primary wiring. Repair or replace as necessary.

4. Inspect the secondary coil wire. Repair or replace asnecessary.

5. Check the tightness of the wiring connections. The secondarywire should be pressed all the way into its socket and theinsulating boot should be in place. Tighten as necessary.

6. Remove the secondary wire from the coil tower. Inspect thewire and coil tower. If the coil tower is eroded due to poorwiring connection, replace as necessary.

NOTE: Corrosion in the coil tower may be cleaned with asmall wire brush.

7. Check the coil polarity.

B. Test the ignition coils.

1. Test the primary resistance of the ignition coils.


b. Disconnect the primary and secondary coil terminals.

c. Connect the DMM to the primary positive (+) andnegative (-) leads.

d. Read the resistance. Compare reading to manufacturer'sspecifications. Replace as necessary.



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2. Test the secondary resistance of the ignition coils.

a. Connect the DMM leads from the primary positive (+)terminal to the secondary coil terminal.

b. Read the resistance. Compare reading to manufacturer'sspecifications. Replace as necessary.

c. Disconnect the DMM.

C. Replace the ignition coils.

NOTE: Manufacturers recommend replacing the ignition coilsinstead of attempting to repair them.

1. Disconnect the primary leads from the ignition coils. Note theposition of the wires for proper reassembly.

2. Disconnect the secondary coil wire.

3. Loosen the coil mounting bracket and remove the ignition coil.

4. Reverse the steps for installation.

IV. Procedures for checking and adjusting ignition timing and timingadvance/retard

A. On EI systems, ignition timing is completely controlled by the PCMand cannot be adjusted. Checking ignition timing is not necessary.If a problem with ignition timing occurs, there is most likely aproblem with the different sensors or PCM.

V. Procedures for inspecting, testing, and replacing the secondary wiring

A. Inspect the secondary wiring.

1. Inspect the wiring insulation for cracking, chafing, oil soaking,or other damage. Replace as necessary

2. Inspect the wire boots for splitting, tears, or missing boots.Replace as necessary.


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3. Check for loose wiring at the spark plugs and ignition coils.Tighten loose-fitting spark plug end terminals by squeezing theterminal lightly with pliers. Be careful not to damage wireboots.

4. Inspect the routing of the spark plug wires.

a. To prevent crossfire, check that spark plug wires areseparate if connected to cylinders that fire consecutively.

b. Crossfire results from induction of voltage in a spark plugwire from the magnetic field surrounding a nearby sparkplug wire. It most commonly occurs when two sparkplug wires that fire adjacent cylinders in the firing orderare routed side-by-side.

5. Check that wires are in their retaining/mounting clips androuted in the original pattern.

B. Test the resistance of the spark plug wires.

1. Connect one DMM lead to each end of the spark plug wire.

2. Check the reading. Compare to manufacturer’s specifications.A typical maximum resistance is 7,000 ohms per foot. Replaceas necessary.

NOTE: Specifications vary greatly. Check manufacturer'sspecifications before passing or condemning a wire.


C. Replace spark plug wires.

1. Grasp the wire by the wire boot and remove by gently twistingand pulling.

NOTE: Do not remove the spark plug wires by pulling hardon the wire because this can break the carbon string.

2. Note the routing of each wire and reinstall the retaining clips.


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3. Install the wires by pushing the wires firmly onto the sparkplug terminals.

4. If the wire boot is the only item that must be replaced,carefully cut the old boot from the wire. Lubricate the newboot with spray silicone lubricant and slide the boot onto thewire. Do not pull on the wire.

VI. Procedures for servicing spark plugs

A. Remove the spark plugs.

CAUTION: It is important to follow the proper procedures whenremoving and installing spark plugs. It is also important to befamiliar with procedures for inspecting spark plugs whenremoved from the engine.

1. Grasp the spark plug wire by the wire boot and remove bygently twisting and pulling. Remove all spark plug wires. Ifnecessary, label the wires with tape to ensure properreinstallation.

2. Use compressed air to blow dirt or other contaminants fromaround each spark plug.

3. Select the proper spark plug socket, a deep-well socket with aspecial rubber insert that protects the porcelain insulator.

4. Remove each spark plug. If any of the spark plugs areexcessively tight, apply a penetrating lubricant to the base ofthe spark plug.

NOTE: Keep the spark plugs in order so that any problemsfound can be traced to the proper cylinder.

B. Inspect the spark plugs.

1. Inspect the condition of the electrodes. Replace as necessary.

2. Inspect the electrode gap. The gap should be set tomanufacturer's specifications.

3. Inspect the spark plugs for fouling. Spark plugs should beclean with no foreign deposits on the insulator or shell.Replace as necessary.

4. Inspect the insulator. Replace as necessary.


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5. Examine each spark plug for any conditions that mightshorten the life of the spark plugs or indicate engine problems.

C. Install the spark plugs.

1. Adjust the electrode gap of each spark plug to specification.Use a spark plug gap gauge to bend the side electrode to adjustthe spark plug gap.

NOTE: Bend only the side electrode. Bending the centerelectrode breaks the insulator and destroys the spark plug.

2. If the spark plugs are the gasket-seat type, check that thegasket is in place.

NOTE: If the spark plugs seemed overly tight when removed,there is most likely excessive carbon buildup on the thread areaof the spark plug and cylinder head. Use a thread chaser toremove carbon buildup.

3. Install the spark plugs finger tight in the cylinder head.

NOTE: When working with an aluminum cylinder head,apply a conductive-type antiseize compound to the threadsbefore installation to prevent sticking or seizing and help withfuture removal of the spark plugs.

4. Tighten spark plugs to specified torque with a spark plugsocket and torque wrench.


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UNIT VI: ENGINE RELATED SERVICE


I. Unit objective

II. Lesson plan

A. Lesson 1: Engine Related Service


2. Job sheets

a. JS1-L1-UVI: Check and Adjust Valve Lash on Engines

b. JS2-L1-UVI: Remove and Replace Timing Belt/Chain

c. JS3-L1-UVI: Inspect, Test, and Service Thermostat andComponents

d. JS4-L1-UVI: Inspect, Test, and Service Fans and FanComponents

e. JS5-L1-UVI: Perform Common Fastener and ThreadRepairs

f. JS6-L1-UVI: Perform an Oil and Filter Change

g. JS7-L1-UVI: Identify Hybrid Vehicle InternalCombustion Engine Service Precautions

B. Lesson 2: Oxyfuel Heating and Cutting


2. Job sheets

a. JS1-L2-UVI: Heat and Cut Metal Using an OxyfuelTorch

III. Unit VI Test


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UNIT OBJECTIVE

After completing this unit, students should be able to perform engine relatedservice. Students will demonstrate mastery of the material by successfullyperforming specific tasks on the job sheets and achieving a score of onthe Unit VI Test.

SPECIFIC OBJECTIVES


Lesson 1

I. Explain the procedures for checking and adjusting valve lash on engineswith mechanical or hydraulic lifters.

II. Explain the procedures for removing and replacing timing belt/chain.

III. Explain the procedures for inspecting, testing, and servicing thethermostat and components.

IV. Explain the procedures for inspecting, testing, and servicing fans and fancomponents.

V. Explain the procedures for performing common fastener and threadrepairs.

VI. Explain the procedures for performing an oil and filter change.

VII. Explain the procedures for identifying hybrid vehicle internal combustionengine service precautions.


A. Check and adjust valve lash on engines (JS1-L1-UVI).

B. Remove and replace timing belt/chain (JS2-L1-UVI).

C. Inspect, test, and service thermostat and components (JS3-L1-UVI).

D. Inspect, test, and service fans and fan components (JS4-L1-UVI).

E. Perform common fastener and thread repairs (JS5-L1-UVI).


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F. Perform an oil and filter change (JS6-L1-UVI).

G. Identify hybrid vehicle internal combustion engine serviceprecautions (JS7-L1-UVI).

Lesson 2

I. Explain the basics of oxyfuel.

II. Identify and describe the components of an oxyfuel outfit.

III. Identify and describe personal protective equipment.

IV. Explain and practice safety procedures.

V. Describe the types of flames.

VI. Explain the factors that affect a cut.

VII. Explain the procedures for heating and cutting metal using an oxyfueltorch.


A. Heat and cut metal using an oxyfuel torch (JS1-L2-UVI).


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LESSON 1: ENGINE RELATED SERVICE

I. Procedures for checking and adjusting valve lash on engines withmechanical or hydraulic lifters

A. Mechanical valve lifters must have clearance (lash) between the camand the valve while the valve is closed. If there is no clearance, thevalve will be held open by the valve train linkage.

1. Methods for checking and adjusting lash vary, depending onthe design of the valve lifter.

a. Some valve trains have adjustable lifters located at thecamshaft.

b. Others have adjusters at the rocker arm that arecomposed of a screw and locknut.

c. A third type uses valve adjusting shims located at the topof the valve stem.

2. Valve lash on mechanical valve trains must be adjustedaccurately when the valve train is assembled. Clearance mustbe maintained by periodic measurement and adjustment.

3. Measure the clearance by inserting a feeler gauge of theproper thickness between the valve train linkage and the valvestem.

a. In some applications, the clearance is measured with theengine running at normal operating temperature. Othersrequire that the engine be cold.


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b. Consult service information for the required clearancedimension and proper adjustment procedures.

B. Hydraulic valve lifters must be adjusted when the valve train isassembled. Clearance is hydraulically maintained and periodicmaintenance is not required.

1. Valve lash is not measured in the same way as clearance inmechanical valve trains.

a. Unlike mechanical valve trains, valve lash is notmeasured as a clearance. Clearance in hydraulic valvetrains is always zero.

b. In hydraulic valve trains, the valve lash is the amountthat the lifter piston is deflected into the lifter body whenthe valve is closed. If there is any measurable clearance,the hydraulic valve train will be noisy. If the pistonbottoms in the lifter body, the valve will not close.

c. If the hydraulic valve train is properly adjusted, the lifterpiston will be about one-half of the way down in thelifter body.

d. Consult proper service information for more specificprocedures.

II. Procedures for removing and replacing timing belt/chain

A. Remove the timing belt/chain.

1. Disconnect the negative battery cable.

2. Remove belts, brackets, hoses, and wiring that interfere withremoving the timing cover.

3. Remove timing cover.

4. Loosen and remove timing belt/chain tensioners.

5. Remove timing belt/chain from the timing gears.

6. Remove timing gears.

7. Clean timing gears/pulley. Inspect for wear or damage.

8. Clean and inspect timing belt/chain tensioner assembly.


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B. Install and adjust timing belt/chain.

1. Install the replacement timing belt/chain.

2. Install and adjust the timing belt/chain tensioners.

3. Turn the crankshaft in the direction of normal rotation twocomplete turns.

4. Verify correct camshaft timing.

a. Verify correct camshaft timing with the valve timingcomponents located in the block (nonoverhead camshaftengines).

1. Observe the valves in the number 1 cylinder.Disassembly may require removing the rocker armcover from the head.

2. Find the timing mark on the harmonic balancer,which is located at the front of the crankshaft.

3. Rotate the engine in the normal direction. Observethe action of the valves in the number 1 cylinder.

• Find the overlap position of the cylinder bynoting when the exhaust valve closes andwhen the intake valve begins to open.

NOTE: The overlap position occurs whenboth of the valves are slightly open at the sametime (one just coming closed and the other justcoming open).

• Position the crankshaft so that the valves arein the overlap position. At this position, thetiming marks should be at top dead center(TDC). If they are not, the valve timing is off.The engine short block must be partiallydisassembled to correct this problem.

b. Verify correct camshaft timing in overhead camshaftengines.

1. Turn the crankshaft to the TDC position.


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2. Remove the camshaft drive cover so that thecamshaft(s) and timing marks can be seen.

NOTE: Some camshaft drive covers have smallopenings that can be used to see the timing markswithout removing the cover.

3. If the timing marks are correctly aligned, inspect thecondition of the camshaft drive chain or belt andgears.

4. If the timing marks are not correctly aligned, timeaccording to manufacturer’s procedures.

5. Reinstall the timing cover.

6. Reinstall the belts, brackets, hoses, and wiring that wereremoved to access the timing belt/chain.

7. Reconnect the negative battery cable.


CAUTION: Be sure to use the approved exhaust ventilationequipment when operating a vehicle in an enclosed area.

9. Start the engine. Check engine operation.


III. Procedures for inspecting, testing, and servicing the thermostat andcomponents

A. Use service information to locate the thermostat.

B. Inspect the thermostat housing and gasket for leakage or damage.

C. Test the thermostat.

1. Verify engine operating temperature. (See Unit II - GeneralEngine Diagnosis, Lesson 3, Section III for the procedures.)

2. Check the circulation within the cooling system.



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b. Start the engine. Take off the radiator cap and lookdown the radiator neck.

CAUTION: Never remove a radiator cap unless theengine is sufficiently cool. Removing the radiator capwhen the engine is hot can cause scalding-hot enginecoolant to be sprayed over a wide area, resulting inserious injury.

c. When the engine reaches normal operating temperature,the thermostat should open. Observe the engine coolantas it circulates through the radiator tank. If enginecoolant overflows the radiator tank, the radiator coremay be plugged.

d. If possible, check the circulation through the upper hosewhen the engine is “gunned” and while the thermostat isopen.


D. Replace the thermostat and components.

1. Drain the cooling system.

2. Remove the thermostat housing and thermostat.

3. Clean the mating surfaces of the thermostat housing andengine, removing the old gasket/seal.

4. Install the new thermostat with the wax-filled pellet towardthe inside of the engine. Center the thermostat in the housing.


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CAUTION: Be sure to install the correct thermostat for theengine. The wrong thermostat can cause enginemalfunction due to being too cold or too hot.

5. Install the new gasket/seal and thermostat housing. Use thecorrect sealer to install the gasket.

6. Refill the cooling system and bleed air, if required.



8. Start the engine and check cooling system operation.


IV. Procedures for inspecting, testing, and servicing fans and fan components

A. Inspect the mechanical (belt-driven) fan.

CAUTION: Radiator fans are very dangerous. Keep hands awayfrom the fan during operation. Disconnect the negative batterycable when inspecting and servicing a mechanical fan. Onlyconnect the negative battery cable when observing fan operation.

1. Make sure the fan runs quietly. Fans should make no growlingor grinding noises.

2. Check the fan for bent blades, cracks, and other defects.

CAUTION: Bent or cracked fan blades may fly out of thefan with great force and cause personal injury.

3. Make sure the fan spins without noticeable wobble.

4. Make sure there is no more than 3/8-in play in the fan.

5. If the fan is a clutch fan, check for signs of oil leaking from theclutch assembly.

B. Test a clutch fan.



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2. Start the engine.

3. Observe fan operation.

a. Before the engine warms, the fan should slip.

b. When the engine warms, the clutch should engage andair should begin to flow through the radiator and overthe engine, indicating that the clutch is locked.

c. A fan clutch that is locked all the time regardless ofengine operating temperature should be replaced. A fanclutch with excessive play or oil leakage should also bereplaced.

4. Shut off the engine and disconnect the exhaust ventilationequipment.

C. Inspect the electric radiator fan.

CAUTION: Electric radiator fans can come on without warning.Make sure the fan and negative battery cable are disconnectedbefore inspecting, servicing, or working close to an electric fan.Only connect the fan and negative battery cable when observingfan operation.

1. Make sure the fan runs quietly. Fans should make no growlingor grinding noises.

2. Disconnect the fan and negative battery cable.

3. Check the fan for bent blades, cracks, and other defects.

CAUTION: Bent or cracked fan blades may fly out of thefan with great force and cause personal injury.

4. Make sure the fan spins without noticeable wobble.

5. Check that there is no more than 3/8-in play in the fan.

6. Using service information, energize the fan and observeoperation of the unit.


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7. Using service information, check the sensors and controls thatoperate the fan.

D. Inspect the fan shroud for cracks or damage, shroud-to-fan fit andclearance, and condition of mounting brackets and bolts.

E. Inspect the cooling system air dams and mounting brackets fordamage.

F. Based on the inspections and tests, repair or replace defectivecomponents. Consult service information for the proper procedures.

V. Procedures for performing common fastener and thread repairs

A. Remove a bolt that is broken off in a threaded hole because ofovertightening.

1. Use a screw extractor to remove bolts. The screw extractor hasflutes or grooves that spiral in a counterclockwise direction.

a. Drill a hole in the center of the broken bolt.

b. Insert the screw extractor in the hole.

c. Use a tap handle to rotate the screw extractor and boltcounterclockwise. Remove both as a unit from the bolthole.

2. Remove a bolt that is not bound to the threaded hole.

a. Drive a sharp punch into the center of the bolt.

b. Use pliers to retrieve the bolt.

NOTE: Breakage due to the wrong thread design,a cross-threaded bolt, or a bolt that is bottomed out in thehole can make removal difficult. Drill out the bolt andretap the hole. Use the correct bolt and start it into thehole with the fingers.

B. Use a tap to cut threads into a hole.

CAUTION: Before drilling a hole to cut threads, choose thecorrect drill bit size for the thread size. Failure to use the correctdrill bit size can result in a broken tap or inadequate threaddepth.


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1. Select the proper tap.

2. Apply thread cutting oil.

3. Start the handle with the tap straight and then make a halfturn.

4. After each partial turn, back the tap off until the metal chipsbegin to break loose.

5. Repeat this process until all of the needed threads are cut.Add oil as needed during the process.

C. Use a die to cut threads onto a rod.

1. Select the proper die.

2. Apply thread cutting oil.

3. Put the tapered side of the die on the rod.

NOTE: A special die stock holds the die for the cuttingprocess. The die should be positioned in the die stock so thatthe tapered end engages the rod first.


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4. Start the die stock with the die straight and then make a halfturn.

5. After each partial turn, back the die off until the metal chipsbegin to break loose.

6. Repeat this process until all of the needed threads are cut.Add oil as needed during the process.

D. Repair damaged or stripped threads.

1. Chasing threads involves using a standard tap or die to runthrough existing threads of the same size. The purpose is tocorrect small imperfections that interfere with the threading ofthe nut or bolt.

NOTE: Use a thread cutting oil during this procedure.

2. When threads in a hole are so severely damaged that theycannot be adequately repaired by chasing, a helicoil can beinstalled to restore the threads back to their original sizes.

a. Completely drill out the old, damaged threads with adrill bit supplied in the helicoil kit.

b. Tap with a special tap from the helicoil kit.

c. With a special handle, screw in an insert that looks like aspring or coil. The inside of this coil is the same as theoriginal thread of the hole.

3. A thread insert can also be used to repair damaged threads.The insert is almost identical to the helicoil but is somewhatlarger. It is retained in place by driving down four pinsaround the insert.

4. Thread repair cement can be used on low-torque applications.The cement is applied to the bolt, and the bolt is then placedback into the damaged hole. New threads are molded as theglue-like substance hardens.

VI. Procedures for performing an oil and filter change

NOTE: This is a general procedure for changing oil. Even thoughchanging oil is a relatively simple task, it is critical that it be donecorrectly. Consult the appropriate service information for specificationsand procedures for changing oil on any particular vehicle.


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NOTE: Be especially careful to consult service information whenchanging the oil on turbocharged vehicles. Vehicles with turbochargersoften require special oil. In addition, procedures for changing oil onturbocharged vehicles may also be more complex.

A. Connect the exhaust ventilation equipment.


B. Start the engine and allow it to reach normal operatingtemperature. Turn off the engine. If the vehicle is turbocharged,allow the engine to idle during the last few minutes of operation.

NOTE: Even if a turbocharged vehicle comes into the shop atnormal operating temperature, start the engine and allow it to idle afew minutes. A warm turbocharged engine must idle in order toscavenge oil from the turbocharger.

C. Lift the vehicle in order to get to the underside.

CAUTION: When lifting a vehicle, always use proper liftingequipment and observe all safety precautions. Never work undera vehicle supported by only a jack. A frame-type lift or safetystand is the only acceptable support for a vehicle. Failure tocomply with all safety rules could result in fatal injuries.

D. Place a drain pan or drain bucket under the crankcase drain plug.

NOTE: Some engines have more than one drain plug, and all mustbe removed to completely drain the oil from the engine.

E. Remove the oil drain plug or plugs and catch the oil in the drainpan or bucket. Allow the oil to drain for a few minutes.

CAUTION: Do not allow hot oil to contact the skin.


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F. While the oil is draining, check the following.

1. Inspect the drain plug, oil pan threads, and drain plug gasket.Replace if worn or damaged.

2. Check the suspension and steering joints in the vehicle andlubricate, if required.

3. Check the grease in the rear axle (or final drive) and thelubricant in manual transmissions.

NOTE: When checking lubrication points, components orsystems that relate to the vehicle’s safe operation should bechecked. These may include suspension components(especially the shock absorber), steering linkages, exhaustsystems, fuel tanks and lines, tires, etc. In addition, tirepressure should be checked and adjusted, as needed.

G. Use an oil filter wrench to remove the oil filter. Catch oil in thedrain pan or drain bucket. Clean the area where the oil filter gasketwill seal and make sure that the oil gasket is not still stuck there.

H. Reinstall the drain plug(s) and tighten securely. Do not over torqueor cross thread the drain plug. Replace worn or damaged gaskets atthis time.

I. Install the new oil filter. Lubricate the gasket with clean engine oil.Tighten the oil filter according to manufacturer’s specifications.Most filters are tightened hand tight. Some have specific torquingtechniques. Consult appropriate service information for tighteningspecifications.

J. Recheck all work and make sure that the drain plug(s) are installedtightly. Also make sure that the oil filter is on tightly.

K. Lower the vehicle to the floor.

L. Select the correct type and weight of oil.


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M. Open the hood and add the proper amount of new oil to the engine.Perform lubrication service under the hood as required. In somevehicles, the throttle and other control linkages should be lubricatedat this time.

CAUTION: Be sure to add the correct amount of oil to theengine. Adding too much or too little oil can result in severeengine damage.

N. Start the engine and allow to idle for a few seconds. The oilpressure warning system may actuate for a few seconds but shouldreset itself within 10 seconds.

NOTE: If the engine does not show signs of developing oil pressurewithin 10 seconds, shut off the engine immediately. Locate andcorrect the problem. Double-check that oil was put in the engine.

O. Allow the engine to idle for a few minutes. While the engine isidling, lift the vehicle and check the drain plug(s) and oil filter forleaks.

NOTE: In turbocharged vehicles, idling is necessary to get theproper amount of oil pressure to the turbocharger before it isactuated. In non-turbocharged vehicles, idling the engine allows theopportunity to check for leaks.

P. Lower the vehicle and record on a windshield/door tag the vehicle’smileage, date, and precisely what service was performed.

Q. Shut off the engine. Disconnect the exhaust ventilation equipment.

R. Dispose of the used oil according to the United StatesEnvironmental Protection Agency (EPA) guidelines.


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VII. Procedures for identifying hybrid vehicle internal combustion engineservice precautions

A. A hybrid vehicle, also called a hybrid electric vehicle (HEV), usesboth an electric motor and a small, internal combustion engine forpower. The two types of HEV designs are series and parallel.

1. In the series design, an electric motor drives the vehicle withpower from a battery pack. The internal combustion engine isused solely to power the generator that, in turn, recharges thebattery pack.

2. In the parallel design, the electric motor and internalcombustion engine both drive the vehicle, with the electricmotor being used when additional power is needed (e.g.,acceleration, going up hill) and the internal combustion enginetaking over at cruising speeds.

B. The thought process behind HEVs is to meet the desire to decreasedependence on oil and lessen environmentally-harmful emissions.

1. At this printing, HEVs are entering the marketplace gradually,but they are in their infancy and technology is still evolving.

2. It is unknown whether HEVs will eventually replace thestandard gasoline-powered vehicles or are primarily an interimstep toward another technology.

3. Currently, the advantages of HEVs are improved mileage andless emissions. Among the disadvantages are morecomplicated designs and heavier vehicles due to the additionalcomponents.

C. Servicing HEVs can be potentially dangerous. Careless service canresult in potentially-fatal electrical shock, arcing temperatures up to3500°F, or explosion of molten metal. It is imperative for thetechnician to know and adhere to service precautions.

1. During service, the technician must wear high-voltage safetygloves similar to an electrical lineman’s gloves when removingthe service plug. The technician should also shield the face.

2. At this printing, high-voltage cables are orange. Also, cautionlabels are used to identify the high-voltage battery pack andother high-voltage components.


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CAUTION: Be sure to identify the high-voltage cablesbefore beginning service. Not all high-voltage cables arebright orange. Some are very light orange and can appearyellow.

3. High-voltage cables can be located near vehicle lift locations.Be sure lift pads are placed properly.

4. Some components contain strong magnets that must behandled with special care. People with pacemakers or othermagnetically-sensitive medical devices should not work on ornear these components. The technician should remove allmetal items from pockets or clothing before beginning service.

5. The high-voltage system should be disconnected beforebeginning service. Disconnecting the auxiliary battery shutsdown the high-voltage circuit. For additional protection, theservice plug can be removed.

6. Wait at least five minutes after removing the service plug toallow the capacitors inside the inverter to fully discharge.

7. Some HEVs automatically turn the engine on and off when theready light, located on the instrument panel, is on. Removethe key from the ignition before beginning service.

D. Identify hybrid vehicle internal combustion engine serviceprecautions.

1. Using service information, determine the locations of the high-voltage system components, including the high-voltage cablesand service plug.

2. Using service information, determine if special care is neededwhen handling any components of the high-voltage system.

3. Deactivate the high-voltage system.

CAUTION: The following procedure is for a Honda HEV.It is imperative to consult service information for the properprocedures for the specific HEV before beginning service.


b. Remove the rear seat back.


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c. Remove the battery module cover from the intelligentpower unit (IPU) lid.

d. Remove the locking cover from the battery moduleswitch.

e. Turn off the battery module switch.

f. Turn the locking cover around and put it back on thebattery module switch.

g. Wait at least five minutes to allow the capacitors insidethe inverter to fully discharge.

h. Remove the IPU lid.

i. Measure voltage at the junction board terminals. Thereshould be 30 volts or less. There is a problem if there ismore than 30 volts.


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LESSON 2: OXYFUEL HEATING AND CUTTING

I. Basics of oxyfuel

A. Oxyfuel is a group of processes in which oxygen and a combustiblefuel gas are combined to make a flame. This flame can reachtemperatures of 5,000°F to 6,000°F, which is hot enough to melt orcut most metals. These processes are used to heat, cut, weld, braze,and hardface metal.

1. In oxyfuel cutting, the fuel gas flame heats the metal and astream of oxygen then cuts the metal. Typical kinds of cutsinclude cutting flat steel, round-bar steel, and cast iron. It isalso possible to bevel and make holes in metal.

B. Fuel gases used in oxyfuel processes include acetylene, propane,natural gas, hydrogen, butane, and methylacetylene-propadiene(MPS). Each has different properties and may not be used for allfunctions or perform them equally well.

1. Acetylene is used because of its versatility in performing manyfunctions well. It can make a clean, accurate cut and theflame it produces is easily regulated. “Oxyacetylene” is a termcreated from combining the words oxygen and acetylene.

NOTE: In this lesson, “oxyfuel” refers to oxyacetylene, but itis important to remember that other fuel gases are available. Ifothers are used, accessories and procedures designed for thosemust be used.

II. Components of an oxyfuel outfit

A. Each outfit has two steel cylinders (oxygen and acetylene) designedto hold gases under high pressure.

1. The oxygen cylinder has a back-seating valve that controls gasflow from the tank. When the tank is in use, the valve isopened all the way to prevent leakage around the valve.

2. The acetylene cylinder valve is only opened 1/4 to 1/2 turnwhen in use, so it can be shut down quickly in an emergency.The device used to open the acetylene cylinder valve must beleft in place during use to allow for quick shutoff.


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3. Cylinders should be fastened to a wall, post, or approvedcylinder truck so they stay upright at all times. The valve canbe damaged and cause a leak if the cylinder is knocked over.To prevent damage, valve protection caps should be in placewhen the cylinder is not in use.

B. Regulators are attached to both cylinders and control the flow ofgases through the oxyfuel outfit.

1. Regulators reduce high-storage pressure to a lower workingpressure and maintain a steady working pressure even if thecylinder pressure changes.

2. A regulator has a cylinder pressure gauge and a workingpressure gauge.

C. Valves are attached to both cylinders and control the flow of gasesthrough the oxyfuel outfit. Valves perform valuable safetyfunctions.

1. A cylinder valve is located at the top of the cylinder and isopened by a handle or valve wrench to adjust the flow of gas.

2. A torch has two valves, one for oxygen and the other for fuelgas, turned by hand to control the gas flow into the torch.

3. Check valves are located at the torch or regulator and preventgas from flowing the wrong way.

4. Some regulators are equipped with safety release valves thatrelease gas to lower excessive pressure.

D. Regulator gauges include the cylinder pressure gauge, whichmeasures pressure in the cylinder, and the working pressure gauge,which measures the pressure going into the line.

1. Gauges indicate pressure in pounds per square inch gauge(psig) or in kilopascals gauge (kPag).

2. Gauges have markings beyond the range of normal or safeoperation. Acetylene working pressure gauges may be markedup to 30 psig, but acetylene pressure should be kept below 15psig for safe operation.

E. An oxyfuel outfit has two hoses, one carries oxygen and the othercarries fuel gas.


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1. Hoses are made of several layers of rubber. They come indifferent sizes according to the hose’s inside diameter. Theyare generally available in two colors: green for oxygen and redfor fuel gas.

NOTE: Hose colors are not standardized and hookup maydiffer from one oxyfuel outfit to another. Check hoses as partof the basic setup procedure.

2. One end of the oxygen hose is connected to the oxygencylinder regulator and the other end is connected to the torch.The fuel gas hose is connected to the fuel gas cylinder regulatorand the torch.

CAUTION: Do not switch the hoses from one fuel gas toanother. This can create a combustible mixture in the hose.

F. A cutting torch is held by the operator to make the cut.

1. The cutting torch mixes oxygen and fuel gas to produce thedesired flame. It is held by the operator to make the cut.Oxygen comes out the center opening in the cutting tip andthe fuel gas comes out another opening(s) in the cutting tip.

2. The components of a cutting torch are the fuel gas valve,oxygen valve, cutting oxygen lever, body, cutting oxygen tube,preheating gases tube, head, and cutting tip.

III. Personal protective equipment (PPE)

A. When using oxyfuel, specific clothing and gear are necessary toprotect the body from sparks, burns, and harmful fumes. The eyesand other body parts must be protected from harmful light rays.

B. Leather gauntlet-style gloves and high-top leather shoes should beworn to protect the hands and feet.

C. Clothing should be wool or cotton. It should be dark and tightlywoven to help block light rays.

1. Shirts should be long sleeved and worn with the sleeves andtop collar button buttoned.

2. Pants should come down over the tops of the boots and becuffless to avoid catching sparks.


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3. Other protective clothing and equipment, such as leatheraprons and leather sleeves, should be worn as needed.

D. Wear welding goggles with filter lenses appropriate for the workbeing done. Lenses with a shade number between 4 and 6 arecommon for oxyfuel cutting.

1. Wear safety glasses under the welding goggles to protect eyesfrom flying debris.

2. Wear additional head and eye protection, such as a flameproofskullcap or face shield, to avoid burns from sparks or hot metalspatter.

E. Respirators may be required depending on the size of the work area,available ventilation, and metals being used.

1. Some types of metals give off toxic fumes during the cutting orwelding process. Metals covered with paint, grease, or otherchemicals can create a breathing hazard.

2. Acetylene can displace oxygen in the air and cause respiratoryproblems.

IV. Safety procedures

A. The work area should be fire resistant. Oxyfuel cutting should onlybe performed in fireproof surroundings, such as concrete floors andwalls.

1. The work area should be clean and free of trash, grease, oil,and other flammable materials.

2. A fire blanket should be available to wrap around a person incase of fire.

3. An appropriately rated fire extinguisher, first-aid kit, andsafety equipment should be kept within easy reach.

4. Aisles and stairs should be kept free of obstacles for quick exitin case of fire.

B. Ventilation is required to protect clothing from becomingcombustible due to saturation with oxygen or fuel gases. Workingoutdoors or in a large shop with high ceilings is best. If this is notpossible, forced ventilation (hoods and exhaust fans) is necessary.


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C. Proper storage and handling of the cylinders is necessary, becausethey are highly pressurized and can explode.

1. Oxygen and fuel gas cylinders should be stored separately. Ifthe cylinders are stored together and a fire starts, oxygen andfuel gas can release and cause a large explosion and/or blaze.

2. The storage area should be made of fire-resistant materials andbe located away from sources of heat and fire. It should belocked and labeled with appropriate warning signs.

3. Fuel storage should be adequately ventilated to eliminatebuildup of fuel fumes in case of a leak.

4. A cylinder should be moved using a hand truck with a safetychain or by tilting it slightly and rolling it on its bottom edgewith one hand on the valve protection cap.

D. Follow manufacturer’s procedures for setup and shutdown of theoxyfuel outfit.

CAUTION: If the oxyfuel outfit catches fire at any time, turn offthe oxygen and fuel gas at the tanks immediately.

1. Use only components designed for the specific oxyfuel outfit.Some components appear similar to those used with other fuelgases, but they cannot be used interchangeably without risk ofexplosion.

2. Check all connections with a leak-detecting solution. Tightenfittings in areas that bubble.

CAUTION: Do not use petroleum-based solutions to checkfor leaks. Do not use grease to lubricate components.These substances can cause a fire in the presence of oxygen.

3. Use only a spark lighter held at an angle to light the torch.The spark lighter should be long enough to keep the operatorfrom being burned by the flame. Position the torch so that thetip is pointing away from the operator, other people in thearea, and combustible objects.

4. The flame must be off before setting down the torch. If work issuspended for some time, the oxyfuel outfit must be shutdown.


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5. During shutdown, close all points where oxygen or fuel gascan escape and bleed lines of any remaining gas to preventundetected leaks in the system.

V. Types of flames

A. The three types of flames produced by an oxyacetylene torch arecarburizing, neutral, and oxidizing. The welder will start out with acarburizing flame and make adjustments to attain a neutral flamefor cutting.

1. The carburizing flame is low-temperature and may add carbonto the cut or weld. In this flame, too much acetylene is presentand three distinct parts of the flame are visible. It is mainlyused for special applications.

2. The neutral flame does not add carbon or burn the work withoxygen. It is considered the best choice for most cutting andwelding. It is a balance of oxygen and acetylene and has aninner core of flame that is rounded on the end.

3. The oxidizing flame is high temperature and may add oxygento the cut or weld. Too much oxygen is present in this flame,the flame is noisy, and the inner cone is shortened. It is notrecommended for most operations because it may burn thework.

VI. Factors that affect a cut

A. The welder should be in a comfortable position that allows freemovement of the torch hand. Also, the welder should be bracedagainst a stable object to ensure a steady cutting movement.

B. The torch is held in different manners depending on the type of cut.

1. To start a cut on an edge, hold the torch so that the flameangles slightly away from the work. The edge will preheatsooner and allow the cut to begin quicker.

2. To start other cuts, hold the torch straight over the point to becut. The noncutting hand can be positioned under the torchand used for a guide while the torch hand controls the oxygenlever and makes the cut.

3. Most cuts are made with the torch at a right angle to the work.A slight leading angle can be used for straight cuts or a greaterangle can be used for cutting thin stock if needed.


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C. The speed at which the torch is moved when making the cut affectsthe appearance of the cut.

1. If the correct speed is used, the drag lines, lines made on theedge during cutting, are nearly vertical and the top andbottom edge are smooth and square.

2. If the torch is moved too slowly, the drag lines are irregularand the stream tends to wander and gouge the cut. The flamecan melt the top edge of the cut.

3. If the torch is moved too fast, the drag lines tend to break, thetop edge may be jagged, and the cut may not go all the waythrough the material.

D. If correct gas pressure is used, the cut should be smooth and the topand bottom edges square. Too much pressure distorts the cut bydishing out the top or pushing out the bottom. Too little pressurecauses the cut to not go all the way through the metal.

VII. Procedures for heating and cutting metal using an oxyfuel torch

A. Cut a straight line.

1. Inspect equipment, materials, and work area to ensure safeand correct operation. Remove items or materials that couldcause a potentially dangerous situation.

2. Position the plate on the worktable and mark a cutting lineusing a soapstone and straightedge.

3. Clamp angle iron to the plate at a right angle, just off thecutting line, to serve as a guide.

4. Set up the oxyfuel outfit according to manufacturer’sprocedures.

5. Light the torch using a spark lighter.

6. Adjust the flame to a neutral flame with and without theoxygen lever pressed.

7. Position the torch over the edge of the metal, with the center ofthe cutting tip in line with the cutting line and angled slightlyaway from the work. The preheat flames should be just abovethe top of the plate. Use the free hand to steady the cuttinghand.


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NOTE: Right-handed operators generally work best fromright to left, left-handers from left to right.

8. When the plate has reached cutting temperature, press thecutting oxygen lever and move the torch steadily across theplate to complete the cut. Make additional cuts if instructed.

9. Shut down the oxyfuel outfit using manufacturer’s procedures.Return materials and equipment to the proper places.

B. Cut a bevel.


2. Position the plate on the worktable and mark a cutting lineusing a soapstone and straightedge.

3. Clamp angle iron to the plate at an angle, just off the cuttingline, to serve as a guide.

4. Set up the oxyfuel outfit according to manufacturer’sprocedures.



7. Position the torch over the edge of the metal, with the center ofthe cutting tip in line with the cutting line and pointed slightlyaway from the work. The preheat flames should be just abovethe top of the plate. Hold the whole torch at the angle of thedesired cut and guide by the angle iron. Use the hand that isnot operating the cutting lever to steady the cutting hand.

8. When the plate has reached cutting temperature, press thecutting oxygen lever and move the torch steadily across theplate to complete the cut. Make additional cuts if instructed.



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C. Cut a circle.


2. Position the plate on the worktable and mark a cutting lineusing a soapstone.

3. Set up the oxyfuel outfit using manufacturer’s procedures.



6. Use the oxyfuel outfit to pierce steel by holding the torch at aright angle to the work with the cutting tip near the center ofthe circle. The preheat flames should be just above the top ofthe plate.

7. When the plate reaches cutting temperature, raise the cuttingtip 1/2 in or more and slowly press the cutting lever.

8. Rotate the torch until the flame cuts through the metal.

9. Lower the torch into normal cutting position and cut out to thecutting line and complete the cut. Use the hand that is notoperating the cutting lever to steady the cutting hand. Makeadditional cuts if instructed.



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