Test prerequisite
The correct fuel pressure regulator has been installed.
- Use the Electronic Parts Catalogue to check whether the correct fuel pressure regulator has been installed for the vehicle:
The regulating function of the fuel pressure regulator must be ensured under all operating conditions. The fuel pump must always be able to generate a fuel pressure that is higher than the pressure that is adjusted by the pressure regulator.
The DME controls the injection period for which the injection rate is adjusted.
The fuel return line is depressurized at engine standstill and ignition key position 0.
The pressure regulator will close at engine standstill and ignition key position 0. The fuel pressure in the feed will be maintained for an extended period of time. A non-return valve will close in the fuel pump. This measure will maintain the fuel pressure in the fuel system. Extended start times are thereby prevented.
- Let the engine run at idle and measure the fuel pressure.
When the measured value is less than the nominal value - 0.2 bar:
- The line cross-sections in the fuel feed are constricted or the fuel filter is plugged, or
- The voltage supply to the fuel pump function is not OK: For example, as a result of high contact resistance (corrosion) in the plug connection between the wiring harness and the fuel pump.