The pump is switched on by the control unit via the fuel pump relay. When the starter is turned on, the pump creates a fuel pressure of about 3 bar.
A protective circuit in the ignition/injection control unit ensures that the pump only operates when the engine is rotating. This interlock circuit prevents escaping gasoline from igniting after an accident.
Electric Fuel Pump Malfunctions
First of all, check the appropriate fuse. If it's OK, the search continues.
Release the pump.
Check if the pump is spinning: Have a helper turn the starter and place your hand on the pump body. If the pump is running, a slight vibration is felt.
If not, then you need to check whether current is supplied to the pump at all.
Check with a voltmeter or a test lamp if there is a voltage of about 12V between both pump connectors (red and brown wire). To take the measurement, your assistant must crank the starter.
If, despite the correct voltage, the pump does not work, then it is faulty - dismantle and replace it.
Removing the locking cover: press the plastic cover (3) from the mounting hole. Disconnect the multi-pin connector (2) on the lid (1). Disconnect the supply and return hoses (5) from the lock cover. Now loosen the retaining ring (4) by turning the screwdriver to the left and remove it.
If there is no current, then the pump relay in the relay box may be faulty (on the suspension strut dome), see the instrument chapter.
Check to see if a click is felt by hand when actuating the starter. If not, then the relay is faulty.
Among the following sources of malfunction should be mentioned: a defect in the wire to the relay or to the pump, a clogged or bent fuel line, a clogged fuel filter.
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