Checking the fuel dispenser (BMW 3 Series E21)

Remove the diode relay and the fuel pump relay from the mounting block.

Connect the contact "87" of the fuel pump relay holder with a wire to the "+" terminal of the storage battery, thus activating the fuel pump.

With the fuel pump running, slowly lift the air flow meter pressure disk manually or with a magnet. You should feel uniform resistance throughout the entire stroke of the pressure disk.

Slowly lower the air flow meter pressure disc and immediately lift it up, resistance should be felt immediately. If the pressure disc does not require any effort to move in any area, this indicates that the fuel quantity distributor distribution plunger is jammed.

Please note that the pressure disc must be able to drop freely.