e30 Help: Fuel Pump not running, car won't start

[Don Plumley]

Any help debugging this would be appreciated:

89 325i. Car ran perfect yesterday. This morning it would not start. We don't hear the fuel pump run when cranking. Here's what we know:

- New battery: Cranks just fine
- New Fuel Filter
- Gas in car according to gauge
- Fuse 11 looks good
- Power at the fuel relay (pin 30 and ground)
- Trigger voltage (pins 86 and 85) when key on
- Jumper the relay (pins 87 and 30), fuel pump runs (but car won't start)
- Tested the relay with 12V, hear contacts click, tried another orange relay
- Swapped a yellow (O2 sensor) relay into the main (white) relay

I'm out of ideas and want to avoid throwing parts at the problem.

What else could be causing the fuel pump not to run?
Should the car run with the fuel pump jumpered and running?

Thank you in advance,

Don (and Curtis)

[TerryBPP]

Can you hear the pump running? If not test for power at the pump. If you're getting power it may just be the pump.

Fuel pumps are common problems on e30's. Mine was located near the driver side rear wheel well. Some have 2 pumps. 1 main & 1 transfer.

[asphaltgambler]

Verify that you have fuel pressure first at the rail.

[Mike Bonkalski]

Crank sensor.

[Don Plumley]

Originally posted by Mike Bonkalski
Crank sensor.

This or something at the DME is sounding like it.

Terry - I get power at the pump when I bypass the relay; it does not get power when cranked.

[TerryBPP]

DME is your culprit then. Its under the drivers seat. Go to r3vlimited.com and pick up a used one cheap.

[Panzer909]

Don, for future reference, try lurking on this BBS: www.e30tech.com

Its always been an invaluable resource for my E30 issues when they occur.

[Don Plumley]

Thanks Johnny - also posted on the question on bimmerforums.

Update:

For grins, replaced the DME/Main relay. No Joy.
Tested the reference sensor, resistance within spec.
Disconnected the DME connector. The pin-outs were not corresponding to my Bentley, so I simply reconnected it.

And the car starts!?!?!

Okay, so that's good. But worrysome that reconnecting the DME harness "fixed" the problem.

But now, when you blip the throttle, the engine rpms drop and then stumbles. Idle Air Stabilizer valve? I cleaned it out a bit, no real change.

More confused now as to why the car wouldn't start, and now does...

[Don Plumley]

AM Bump:

So the non-start condition is now a stumble on tip-in: I'm thinking vacuum leak.

(Terry - the DME is under the dash on the Pax side on these cars.)

[Panzer909]

Don, did you spray brake cleaner on the vacuum connections to test for your suspected leak? I did this and the idle jumped when spraying no less than three different areas. Easy to replace & rectify on these cars.