Fuel Pump Wiring

Post Mon Jul 04, 2005 9:23 am

Have an E34 Loom in my bay and cant seem to sus out the fuel pump wiring

any good diagrams? the haynes one is pants.

Post Mon Jul 04, 2005 9:51 am

This for a M50 in an E30?
I've done one of these with an E34 loom. What exactly do you want to know?

Post Mon Jul 04, 2005 11:14 am

basicaly unsure of the wiring !

On the e30 loom there is a plug at the steering column... what is this for??

I have managed to follow the haynes manual for the wiring diagrams for the engine plug and can get fuel to pump through if i bridge the relay but its not operating by its self.

When i removed the loom from the e34 it had a 3rd party alarm connected to the fuel pump wiring at the relay. Perhaps i have missed something.

M

Post Mon Jul 04, 2005 11:38 am

" On the E30 loom there is a plug at the steering column. " The E30 engine loom has the ECU mounted to the right of the steering column, and there are two sockets,one whitw and one black, there as well, normally unused. No relevance to the fuel pump.

The E34 engine loom has a green/purple wire to pin 13 of the original E34 engine connector plug (C101 equivalent).
this should connect to pin 13 of the E30 C101 engine socket, also green/purple. This wire goes to fuse 11 of the E30 fuse box, and then back to the fuel pump.
The blue relay on the E34 loom is the fuel relay, and has the green/purple wire going to it.

Post Mon Jul 04, 2005 11:44 am

By process of elimination its more than likley to be an earthing issue...

What threw me was the E34 loom has a lead that goes into the car on a 2 pin plug which operates the fuel pump....

Cheers brian.

Post Mon Jul 04, 2005 11:45 am

You say the fuel pump runs if you bridge it's terminals.
Does the engine run?
The coil of the fuel pump relay (85,86) is powered by a red/white wire to 86, which should have 12V+ from pin 87a of the DME relay, and pin 85 goes to pin 1 of the ECU by a brown/green wire, which is earthed by the ECU to switch onthe pump.

Post Mon Jul 04, 2005 11:47 am

m1key wrote:
What threw me was the E34 loom has a lead that goes into the car on a 2 pin plug which operates the fuel pump....

Cheers brian.

It shouldn't. What colour are these wires?

Post Mon Jul 04, 2005 11:55 am

green/purple and brown/black.

Possibly for an alarm system ??

Does the +12v red/white feed come from the passenger compartment ?

Post Mon Jul 04, 2005 12:02 pm

m1key wrote:green/purple and brown/black.

Possibly for an alarm system ??
Green/purple is the right colour for the fuel pump, don't know what the brown black is, but the colour suggests something should work if it's earthed. Does your E34 loom have the green purple at pin 13 of the engine connector?

Does the +12v red/white feed come from the passenger compartment ?

Red/white wire comes from the white relay beside the fuel pump relay (DME relay). This relay needs to be energised as well for the pump to run.

Post Mon Jul 04, 2005 12:11 pm

Yeah pin 13 is the fuel pump and all is fine in that respect.

Im at work just now so ill get the multi meter on it this evening.

I think it will be no earth or no +12v feed to the other relays.

(the lead that went in to the passenger compartment (E34)had a blanking cover on the plug. If you apply +12v pump runs constantly.)

Post Mon Jul 04, 2005 12:31 pm

The coils on all three relays are earthed by the relevant pins of the ECU.
Pin 1, brown/green for fuel pump, pin 27, brown, for DME relay, and pin 38, brown/green for lambda sensor relay.
I should be at work as well (skiving). Just having a bite of lunch, then I'm off.

Post Mon Jul 04, 2005 12:37 pm

its so frustraiting im at work and i want to be sorting my car. the +12v does not come from the passenger compartment does it ??

hmmm was a few wires on the e34 that went into the car i didnt bother to trace

the car fired up bur just revved high and cut out due to lack of fuel i guess.

Post Mon Jul 04, 2005 12:43 pm

The 12V+ comes via a thick red wire direct from the battery into the E34 engine loom wiring box. There is a joint inside the box, and one branch goes to the white DME relay. When this relay engages, it feeds power from 87a to the fuel pump relay a few inches away, via a red/white wire.
Don't know what these wires into the engine compartment are.
I've stripped two M50 E34s and an E36 and the engine looms are all self contained. My wiring diagrams show self contained as well, with no options shown like you describe.

Post Mon Jul 04, 2005 12:59 pm

Need to get the multimeter on it tonight.

Thanks for the info.

Ill get this done tonight.

M

Post Mon Jul 04, 2005 6:32 pm

found the problem.. brown/green from pin 1 goes to a plug which has brown & green/white & brown & white

i applied +12v to the brown& green and this got the pump up to preasure & the ECU "clicked"

Post Mon Jul 04, 2005 7:00 pm

disregard that, it was just my dodgey wiring.

works fine now as it should. it is indeed self contained in the loom :lol: