Mercedes-Benz W201 fuel pump not running – pump relay
W201 fuel pump not running or car stalls, which relay is the cause?
A typical fault is the fuel pump relay: the solder joints on its circuit board crack, so the pump gets no power even though the relay clicks. The symptom is often the car stalling when warm, or no hum from the pump when the ignition is switched on.
Where is the W201 fuel pump relay and how can it be repaired?
The relay is behind the plastic cover behind the battery, a black box the size of a cigarette pack. The solder joints are resoldered and the old solder is sucked away. Also resolder the neighbouring YJ relay, since the pump relay gets its power through it. A new relay is the surest option.
How can I test the W201 fuel pump?
Remove the pump relay and connect its terminals 30 and 87 with a jumper wire: if the pump runs, the fault is in the relay or its control. The pump then runs continuously, so do the test only briefly. Also check the fuses and contacts. The pump turning alone does not prove sufficient fuel pressure. Remove the jumper immediately after the test and watch out for fuel leaks and sparks.