Merc E220 erratic starting problem
 

Merc E220 (1995 model) erratic starting problem: My car starts 90% plus of the time, no problem. However, every now and again, mostly after a short trip, with a short break after switching off, it refuses to start. Mostly there's nothing when you turn the ignition, but sometimes there's an electrical whirring sound, and yet other times the motor swings but the car fails to start. Then, when you leave it for (say) an hour or longer, it starts perfectly again! Therefore, it is clear that this is not a battery problem. The problem is difficult to fix, because every time it goes to the dealer workshop, they can't imitate the symptom. They have now replaced a relay, and the starter motor, but the problem is still there. Can anybody help, please.

HI Erik

Which relay did they replace? I'm thinking either fuel pump relay or overvoltage relay is causing your problem. If I had to guess I would say fuel pump relay on this one.

fasthair

'Electrical wirring sound' from underneath the right side back seat is the fuel pump. It should run for about half a second each time the ignition is switched on then stop. It runs again when the engine is cranked and when it is running. If not, fuel pump relay is faulty. It's a common problem.