Diesel fuel injection system checks (Mercedes-Benz S-Class W220)

Before you begin working, read the safety precautions in Section Relieving pressure in the fuel system of a gasoline engine.

1. If you detect a fault in the fuel injection system, first make sure that all connectors are securely connected and that there are no traces of corrosion on their surfaces. Then make sure that the fault is not caused by neglect of regular maintenance (check the air cleaner, valve clearances, cylinder compression, fuel filter). Also make sure that the crankcase ventilation hoses are not blocked.

2. If after the above checks the cause of the malfunction is not found, take the car to a service station for diagnostics. At the bottom of the dashboard on the driver's side there is a diagnostic connector to which special diagnostic equipment is connected. This equipment reads the fault codes recorded in the control unit's memory.

3. Error codes can be read using a special diagnostic scanner available at the service station, or a personal computer with a special board, program and cable.

4. By reading the codes, you can easily detect a malfunction, even if it is not obvious. You can check any unit without using a diagnostic code scanner, but keep in mind that unprofessional intervention in the system can lead to damage to electronic units.

5. If you have a diesel tachometer or other suitable equipment, you can measure the idle speed. However, these parameters cannot be adjusted. The cause of the idle speed deviation may be faulty injectors. In this case, they must be cleaned and calibrated. The service life of the injectors is unlimited, but it may happen that you will have to repair or replace them after a run of approximately 100,000 kilometers. Repair and calibration of injectors should be performed by a specialist.