5 Series E60 M5 (S85) SAL
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Notes on fuel pressure check (reference pressure: environment)
Feature of this version with ambient pressure:
The connection for the vacuum hose of the fuel pressure regulator is located between the throttle and the air
cleaner or on the air cleaner.
The correct fuel pressure regulator is fitted.
Using the EPC, check whether the fuel pressure regulator suitable for the car is fitted:
Connect test adapter.
Description of operation:
The control function of the fuel pressure regulator must be guaranteed under all operating conditions. The fuel pump
must always be able to generate a higher fuel pressure than the pressure regulated by the pressure regulator.
The injection rate is adjusted by means of the injection time; the injection time is controlled by the DME.
Description of operation: fuel return line
When the engine is at a standstill and the ignition key is in position 0, the fuel return line after the pressure regulator is
at zero pressure.
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,
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
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.
With less likelihood, the return line may be completely blocked. When the pressure regulator is removed, fuel could
RA Notes on fuel pressure check (reference pressure: environment)
BMW AG - TIS
Issue status (12/2007) Valid only until next DVD is issued
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