Complaint: Drive Characteristic Faults, Lack Of Power
WARNING: This page is about a different car, the 2005 BMW 645Ci and 2004 BMW 645Ci. However, it is still accessible from the selected car via links, so may be relevant.
- 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.