Gasoline engines
Note: In a diesel engine, the fuel pressure is measured in the fuel line between the filter and the fuel pump. To perform this work, you must contact the workshop.
Ensure that the workplace is well ventilated. Fuel vapors are poisonous, no open flame, do not smoke, fire hazard! Prepare a fire extinguisher.
A prerequisite for a correct check is that the battery is in good condition and charged.
Loosen the clamps and disconnect the fuel outlet hose -2- from the distribution manifold.
Attention: The fuel supply system is under pressure. Collect escaping fuel with a cloth. After releasing the clamps, always replace them with new ones.
Note: On some models, the fuel supply line is screwed directly onto the manifold. In this case, during installation, the sealing ring must always be replaced with a new one and lubricated with technical petroleum jelly. Another possible design is the fastening of hoses with clamps. In this case, the special tool BMW 16 1 050 is required to release the clips. Check sealing ring before installing, replace damaged ring.
Lower the fuel outlet hose from the distribution manifold into a measuring container with a volume of approximately 2 liters.
Remove the fuel pump relay. The fuel pump relay is located in the relay box located at the rear left of the engine compartment.
Connect terminal 30 with a jumper with a diameter of 1.5 mm to terminal B7b on the relay base and turn on the fuel pump for about 30 seconds, see chapter "Checking the fuel pump relay".
The performance of the fuel pump in 30 seconds should be approximately 1 liter. (The current consumption of the pump is a maximum of 9.5 amperes).
If the pump performance is too low, replace the fuel filter and check the pump performance again. If the pump performance is still low, replace the fuel pump.