fuel pump

[PLJ8]

The fuel pump on my 1988 735i wont run. Have tested the pump and all is OK,the problem seems to be at the relay,I have power to it but it wont give me an earth. If I use a jumper across the terminals all is ok if I try to force an earth I get a warning message ref the auto transmission. Can anyone help?

[jeffreyb4me]

the relays [fuel] are controled by the DME unit. make sure you have spark[carefully] and the injectors click. also, two of the relays pins should have B+ when cranking the engine [one powers the relay & the other powers the relay coil which is grounded by the DME control unit. since you've got any power to the fuel pump relay, i'm assuming the 'main' relay is good. AND check the fuel pump fuse [it's listed in the box cover] with the engine cranking.

[PLJ8]

Thanks, I think you have hit the nail on the head as the relay coil is not getting a ground from the DME.Every thing else you mention is fine.Any further thoughts on the matter?

[jeffreyb4me]

IF you do have spark AND the injectors sound like they're clicking with it cranking over [ listen with a long screw driver, tip on an injector or it's connector, handle on your ear ], AND your SURE the fuel pump relay's GOOD, the DME is 'seeing' everything it needs to start the engine, EXCEPT turning on the fuel pump. Unusual but i think i've seen it before. AGAIN, make sure EVERYTHING else is present. I just had a silly thought about your OBC being locked in 'CODE' [driver input anti-theft] but that keeps the MAIN relay from energizing. This advise is only worth what it cost you but it sounds like you've a failed DME control unit.

[PLJ8]

Thanks for the advice,I agree,I think I have a DME problem!