I am looking for some advice - my '86 740 GLE (gas,non-turbo engine) quit on me while I was driving. I checked the fuel supply and there is no fuel pressure and the fuel pump isn't running. I took out the fuel pump relay and jumpered pins 3 and 87/2 and the fuel pump runs but the car still won't start. I tried a known good relay and the fuel pump doesn't run with the good relay. Any tips on further diagnostics? Is there a way of testing the ECU? BTW - where is the ECU located on this car?

 

The ecu is under the dash on the passenger side.
A power stage can do the same thing.
A speed sensor can do the same thing.

 

Thx - any tips on testing the power stage or speed sensor?

 

Just to clarify - even with the good relay the fuel pump doesn't run at all when I turn the key on.

 

Then I would check for power at the pump. It should atleast come on for about 30 seconds.

I don't have the spec's home maybe someone does that they can give you for the power stage.

The speed sensor you should be able to read on ohms and make sure they move up and down while cranking the car.