Description of operation: pressure retaining function
The pressure regulator closes when the engine is at a standstill and the ignition key is in position 0. The fuel pressure in the delivery line is retained over an extended period. A non-return valve closes in the fuel pump. These measures help to retain the fuel pressure in the fuel system. Extended starting times are thus avoided.
Complaint: drive characteristic faults, lack of power
- Run engine at idle speed and measure fuel pressure.
If the measured value is less than the nominal value - 0.2 bar:
- Line cross-sections in fuel feed are constricted or fuel filter is clogged, or
- Fuel pump voltage supply is not O.K.: e.g. as a result of high contact resistance (corrosion) in plug connection between wiring harness and fuel pump.
If the measured value is greater than the nominal value + 0.2 bar:
- Turn off engine stop and then observe measured value.
- If measured value drops to nominal value, then line cross-sections in fuel return are constricted or clogged.
- Check the fuel lines for kinks.
If no kinks are visible:
- Replace return lines
If measured value remains too high, then pressure regulator is in all probability faulty.
IMPORTANT:
With less likelihood, the return line may be completely blocked. When the pressure regulator is removed, fuel could escape under pressure!
- Have a cleaning cloth ready and catch and dispose of escaping fuel.
- Replace the return line but not the pressure regulator.