Fuel Pump Delivery Rate Check

Gasoline Engine

* On diesel engines, check the fuel pressure in the line between the filter and the high-pressure fuel pump (HPFP).
Always ensure the work area is well ventilated. Fuel vapors are toxic. Do not use open flame and do not smoke. Fire hazard! Keep a fire extinguisher ready.

A fully charged and serviceable battery is required for an accurate test.

PROCEDURE
1. Disconnect the fuel return hose (2) from the fuel rail, after opening the clamps. Refer to the accompanying illustration.

* The fuel system is under pressure. Wipe up spilled fuel with a rag. Replace the clamps with new ones during installation.

* On some models, the fuel supply hose is connected directly to the fuel rail. When installing, always replace the O-ring with a new one, lubricated with petroleum jelly beforehand. Other designs secure the fuel hoses with clips. In this case, special tool BMW 16 1 050 is required to remove the clips. Before installation, inspect the O-ring. If damaged, replace it.

2. Route the fuel return hose from the fuel rail into a measuring container with a capacity of approximately 2 L.
4. Disconnect the fuel pump relay. The relay is located in the relay box at the rear left of the engine compartment.
5. Using a 1.5 mm diameter wire, jumper terminals 30 and 87b at the relay base and energize the relay for approximately 30 s. Refer to the Fuel Pump Relay Check section.
6. In 30 s, fuel pump delivery should be approximately
1 L. (Pump current is approximately 9.5 A).
7. If delivery is lower, replace the fuel filter and test the pump again. If delivery is still low, replace the pump.