Electrical Gremlins took over my fuel wiring

[Erick]

So yeah.... quick and simple:

1985 318i
Problem - Fuel pump doesnt turn on.... no fuel even reaches the pump itself.

Fuel pump fuses OK
Fuel pump relay replaced
Fuel pump itself replaced

Any other ideas?
- Erick

[PeaveyBassist]

Wiring between pump and relay/fuse. Possibly the ground.

Will

[E304life]

Check the power and ground, to do this;

Power-check power wire, use a volt/ohm meter and check for 12v at the power wire with the engine cranking.(one probe at the power wire one on a known good ground)

Ground-switch to ohms, turn the key off put one probe on the ground wire and one on a good ground(some unpainted metal on the car works for a ground) should have less than 3ohms resistance.

This is were I would start, report back with your findings.

[Erick]

Sorry to bring this one back to life a month later, but I finally got ahold of a test light and I was playing around with the 318i to try to figure it out.

Anyhow, the fuel pump is not getting any power... the ground is fine. I know the fuel pump wire is brown and the brown wire at the relay isnt getting any power either.

The fuse isnt getting any power either.

Any suggestions?

- Erick

[E304life]

What is you production date and what fuse number are you looking at?

[Erick]

I checked the door stickers and it doesnt mention the production date.... I have the VIN if anything. But the car was sold as an 1985.

I am looking at fuse 11, which does not get power with the key in the ON position.

- Erick

[netcsk]

Vin works fine for figuring out prod date. http://www.bmw-z1.com/VIN/VINdecode-e.cgi

Are you getting spark? If so, ignore the below.
Check that the main relay is getting power. You should also feel it click (and hear it if you listen closely) when the key is turned to the on position. If you don't and you're getting power then your relay is bad (this is why you check it's getting power -- the switched power is a green wire on my eta). If the relay doesn't switch over and you don't have power to the relay, you need to start looking back at the ignition switch.

[Erick]

Which relay are you talking about? The fuel pump relay has been replaced.

Production date 1985 / 05

Good link. Thanks a lot.

[E304life]

netcsk is right, it would be a good idea to check if you have spark, if you have spark then you know you are dealing with a fuel problem if you do not have spark then you are dealing with a power supply or dme input problem.

btw fuse11 is powered by the fuel pump relay and the relay is controled by the crank shaft sensor.

Post back with more questions.

[Erick]

well.... how would not getting spark relate to not getting power in the fuel pump?

[E304life]

If you were not geting fuel or spark then more than likely the dme is not giving the command to activate the fuel pump/injectors and the coil.

If this is the case then more than likely the dme is not seeing a input to fire them off. Or one of the relays like the main relay is not poweing the dme at all.

If you do have spark and no fuel then more than likely you have a isolated problem in the fuel pump circut.

[E304life]

bth nice paint job and wheel combo in your signature car.

[Erick]

Oh I get it now.

I'll check that out then.

Edit: That's the fun car... hehe.... the daily is completely different car.

[Erick]

Ok, I have spark when I try to start the engine.... so where should I look now?

[E304life]

Well go back to the fuel pump relay and check the big red wire at terminal 30. See if there is power there with the key on.

Next moved to the vilot/red wire at terminal 87b while cranking there should be 2 or less volts there. If you do not have a volt meter then pay attention to the intensity of the light from the test light.

If this sounds too complicated you could just try jumping power from terminal
30 to 87b this will bypass the control side of the fuel pump relay and test the
work side(fuel pump circut) side.

If you get fuel pump activation then there is a problem with the fuel pump
relay(not likely if you already replaced it) or the control side of the relay.

Report back with your findings.