Mercedes-Benz W202 petrol engine won't start: fuel pump and relay
My W202 petrol won't start. How do I check the fuel pump?
Switch the ignition on and listen for the pump hum. Make sure there is fuel in the tank and that fuel comes out of the filter's inlet pipe. If the pump gets power but does not work, the fault is in the pump. Otherwise check the relay, its socket and the fuse.
Where is the W202 fuel pump relay?
The relay is in the fuse box in the boot near the battery, next to the spare wheel on the right. It is green and its fuse is 30 A. The overvoltage protection relay is in the boot next to the control units. The relay needs no adjustment; the old one is simply replaced with a new one.
Why does my W202 stall or start poorly even though the pump hums?
The relay can click but only switch the power on intermittently; replacing the relay has fixed this. Other causes are a worn pump, a leaking pressure regulator and a dead overvoltage protection relay. In a saddle tank the fuel may not move to the pump side, in which case adding extra petrol helps.