Note: On diesel engines, the fuel pressure is measured in the fuel line between the filter and the high pressure fuel pump, which can only be carried out at a workshop.
The test condition is a normally charged battery.
Disconnect fuel feed hose 3 from distributor pipe (on a diesel engine - from a high pressure fuel pump) and lower the hose into a measuring vessel with a capacity of approx. 5 l).
Pull out the fuel pump relay. The fuel pump relay is located in the relay box at the right rear of the engine compartment. The fuel pump relay is brown on 520i/525i/524td models and orange on 530t/535i models.
Jumper terminals 30 and 87 on the relay site with a short jumper with a diameter of 1.5 mm and start the fuel pump for about 30 seconds.
In 30 seconds, the amount of fuel supplied should be 875 cm3. In this case, the consumption of the fuel pump is 5 amperes.
If less fuel is supplied, replace the fuel filter and check pump performance again. If performance continues to be poor, replace the fuel pump.