Fuel injection system adjustment - general inormation

Fuel system: single-point injection models / Fuel injection system adjustment - general inormation

1 If a fault appears in the fuel injection system first ensure that all the system wiring connectors are securely connected and free of corrosion. Then ensure that the fault is not due to poor maintenance; ie, check that the air cleaner filter element is clean, the spark plugs are in good condition and correctly gapped, the cylinder compression pressures are correct, the ignition timing is correct and the engine breather hoses are clear and undamaged, referring to Chapter 1, Chapter 2 and Chapter 5B for further information.

2 If these checks fail to reveal the cause of the problem the vehicle should be taken to a suitably equipped VW dealer for testing. A diagnostic connector is incorporated in the engine management system wiring harness, into which a dedicated electronic test equipment can be plugged. This equipment is capable of “interrogating” the engine management ECU electronically and accessing its internal fault log.

In this manner, faults can be pinpointed quickly and simply, even if their occurrence is intermittent. Testing all the system components individually in an attempt to locate the fault by elimination is a time consuming operation that is unlikely to be fruitful (particularly if the fault occurs dynamically) and carries high risk of damage the ECU’s internal components.

3 Experienced home mechanics equipped with a tachometer and an accurately-calibrated exhaust gas analyser may be able to check the exhaust gas CO content and the engine idle speed; if these are found to be out of specification, then the vehicle must be taken to a suitably-equipped WV dealer for assessment.

Neither the air/fuel mixture (exhaust gas CO content) nor the engine idle speed are manually adjustable; incorrect test results indicate a fault within the fuel injection system.