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Technical News BulletinDENSO Diesel systems & diagnostics

Issue 6

In this issue:In this sixth news bulletin we bring you an overview of DENSO Diesel Common Rail Trouble Shooting, as useful background information to our latest film on click here.

DENSO EUROPE B.V.

Hogeweyselaan 165 | 1382 JL Weesp | The Netherlands

Tel. +31 (0)294 - 493 493 | Fax. +31 (0)294 - 417 122

Following the introduction of the new DENSO-C diagnostic tool in our December newsletter, we have issued some additional technical news bulletins in recent weeks to provide further technical insight into DENSO Diesel systems – and the need for, and use of, diagnostics.

DENSO Diesel Common Rail Trouble Shooting (example) In early winter a six year old 2.0L Diesel vehicle (equipped with DENSO Common Rail high pressure Fuel Pump and Injectors) has become more difficult to start than usual. With the engine taking significantly longer to crank, and rough idling just after a cold start, the car is taken to a garage for investigation.

When the car arrives, the receptionist or mechanic takes the most important first step to solving the problem: ensuring that the customer‘s explanation is fully understood. They ask questions that will help to narrow down the possible system malfunction, whilst making educated guesses based on the symptoms.

Example continues overleaf

Technical News Bulletin | Issue 6 Page 2

The next morning, the mechanic uses the moment of cold start to confirm the problem description (according to the circumstances indicated) and to collect relevant data from the engine management system (EMS).

Before starting the engine, he attaches the DENSO diagnostic tool to the vehicle. The mechanic selects the relevant data parameters for the injectors. These are principally injection learn values, engine temperature and rpm.

To come up with a conclusion the data parameters are analysed, both when the engine is running at cold start, and at normal operating temperature. If the revised injection volume difference is found to be high (cold and warm engine), he will decide whether to have the injectors checked at a DENSO Diesel Service Dealer.

When (re)installing the injectors, as always, he follows the procedure as indicated in the OEM- or DENSO repair manual.

He refers to the DENSO repair manual for removing and reinstalling (pumps and injectors) which comes with the DENSO diagnostic tool.

Now the six year old 2.0L Diesel vehicle is starting and idling perfectly – even at cold weather conditions during a cold start!

On this occasion, when the mechanic attaches the DENSO diagnostic tool, no Trouble Codes (DTCs) are found in the engine management system (EMS). There are two trouble shooting sections in the diagnosis manual that comes with the DENSO diagnostic tool: DTC-based, and symptom-based, trouble shooting. In this case the mechanic needs to gather further trouble shooting information from the symptom-based trouble shooting section, selecting the subject ‘Incorrect First Idle’ based on the problem description.

Before carrying out any planned trouble shooting, however, the mechanic carries out the essential check on the vehicle’s basic engine conditions (compression, glow system etc.). Any irregularities found in the basic engine conditions will be fixed first. He also keeps in mind that some basic problems can cause the symptoms described.

When starting the trouble shooting process, he follows DENSO’s recommendation of confirming the problem in detail, based on the customer’s detailed feedback. He knows that if the vehicle has just arrived at the garage it is very likely that the engine is at normal operation temperature; whereas the problem occurs on cold starting! Therefore he starts the trouble shooting the following morning.

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DENSO EUROPE B.V.

Hogeweyselaan 165 | 1382 JL Weesp | The Netherlands

Tel. +31 (0)294 - 493 493 | Fax. +31 (0)294 - 417 122

Technical News Bulletin | Issue 6

www.denso-am.eu

Go online!Over the past few weeks we uploaded some new videos on the DENSO Diagnostic YouTube channel to support these news bulletins. Why not take a look? To check out our films and subscribe to our channel, click here. Thank you for watching!

Scan the QR Code with your smartphone to open the DENSO Diagnostic YouTube channel and have a look at our latest technical movies.

Did you know...?That the revised injection volume as read by the diagnostic tester when the engine is not running, represents the last revised value from the moment that the engine was running – which could be the day before.

Since it could be the previous day when the engine was at normal operating temperature, always start the engine and immediately read out the revised injection volume – before the engine warms up.

Cold Engine Warm Engine

Possible problem causesFuel intake spring clamp:• A common problem when replacing the high pressure fuel

pump, is that the intake spring clamp on the pump inlet will become too loose

• The result of a too-loose spring clamp is that it will allow air ingress into the fuel system, which may cause a difficult start at cold temperatures.

• DENSO recommends always renewing the spring clamp to avoid problems

Starter Motor:• If there are longer periods of difficult start-ups, the starter

motor will suffer extra wear. A worn starter motor could also make the engine being hard to start. This can be diagnosed via the engine RPM during cranking. (If the rpm is too low, it can point to a worn starter motor)

Cleanliness: The highest priority!• When working on a Common Rail System, maintaining

cleanliness is absolutely essential

• The smallest particles may cause engine operating and/or fuel system faults

• During any repair activities, opened fuel connections must be sealed off immediately

• Because of cleanliness and safety issues, do not open the high pressure pump or injectors. (Only the DENSO Common Rail Service Dealers are authorised to judge and replace the inside parts)