Petrol engines
Note: In a diesel engine, the fuel pressure is measured in the fuel line between the filter and the fuel pump. This work should be done at a workshop.
Ensure perfect ventilation of the workplace. Fuel vapors are toxic, no open flames, no smoking, fire hazard! Prepare a fire extinguisher.
A prerequisite for a correct check is a working and charged battery.
Loosen the clamps and disconnect the fuel outlet hose "2" from the distribution manifold.
Caution: The fuel supply system is under pressure. Collect any leaking fuel with a rag. Always replace the clamps with new ones after loosening them.
Note: On some models, the fuel supply line is screwed directly to the distribution manifold. In this case, when installing, the sealing ring must always be replaced with a used one and lubricated with technical petroleum jelly. Another possible design is to fasten the hoses with clamps. In this case, a special BMW tool 16 1 050 is required to release the clamps. Check the sealing ring before installing, replace a damaged ring.
Place the fuel drain hose from the distribution manifold into a measuring container with a capacity of approximately 2 liters.
Remove the fuel pump relay. The fuel pump relay is located in the relay box, located on the left rear of the engine compartment.
Connect terminal 30 with terminal B7b on the relay base using a 1.5 mm diameter jumper and turn on the fuel pump for about 30 seconds, see chapter "Checking the fuel pump relay".
The fuel pump output should be approximately 1 liter in 30 seconds. (The current consumed by 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.