No power to GROUND on the coil.

[BoostedGT]

My first bmw. My first post.

86 325e 5-speed.

She won't start, but cranks over.


Checked for fuel by removing the fuel line, saw fuel.
Checked for fuel by removing the cold start injector, saw fuel.
Plugs are fouled.
All the fuses seem good, removed them one by one.

Checked the coil with a ohm meter and saw theres no power to the ground lead, however theres power to the positive lead.


P.S. Prior to the no start she had a rough idle and stumble through out 700-2500rpm.




What do I look for next?

[PiercedE30]

Try replacing the coil if that is where you think the problem is.

[BoostedGT]

Using the ohm meter on the coil: If I put one lead on +(coil) and the other on the -(coil) I get no reading. Now if I ground to the car I get a reading.

Basicly what I'm trying to say is the wire that is used for ground on the coil is dead.

[BoostedGT]

A few pics that give a better understanding:


















Which one's the main relay: 1 2 3

[rs4pro3]

the coil is triggered by a very fast switching ground, so unless the engine was running you wouldn't see anything. And the main relay is the one on the left(should be the only 5 terminal one)

[jlevie]

rs4pro3 has it right, but to elaborate:

The (+) lead on the coil is hot when the ignition is on. The (-) lead goes to the DME and is grounded by the DME for each firing pulse. When cranking the engine you should see a fluctuating voltage between the (-) terminal and ground if the DME sees timing reference information and the DME is good and has power from the main relay.

[BoostedGT]

Thanks for the help so far.

If I don't see fluctuating voltage while cranking can I say that the DME is bad?

Either way I have to wait till a second hand comes to crank while I check the voltage.

I understand that I can use a "jumper wire" on the main relay to see if its bad, but on what pins? I've searched but no luck so far. Anyone know.

[BoostedGT]

Progress so far...

Well there was no fluctuating voltage while cranking it over.

I removed fuse #11, cranked it with the spark plug on the wire and saw spark. This tests if the crank sensor is working.

Then I put the fuse back in cranked it and there was no spark.

Does this look like a coil problem?
Or is it a main relay problem?

[rs4pro3]

check for voltage coming out of the main relay, which would be a red/blue wire I believe coming from pin 87 and 87 a on the bottom of the relay. To jumper the relay you have to bridge pin 30(constant 12volt) to both pins 87.

[BoostedGT]

Progress so far... she started and drives!

Jumping the main relay did nothing for me. However I jumped the fuel pump relay and she started up fine. BUT if I remove the jumper and put the relay back in she won't start at all, just cranks over.

Time to do a search.

Thanks to all the people who helped, I will keep you updated as alot of search's go off topic -maybe this one might help someone out in the future.

[BoostedGT]

P.S. Prior to the no start she had a rough idle and stumble through out 700-2500rpm.

The rough idle and stumble is gone.

I take it that I need a new fuel pump relay? yes, no?

[euroshark]

Yes, also check your fuses. The E28 has a fuse for the fuel pump as well as a relay... Mine died and did exactly what you describe.

[BoostedGT]

Will check, thanks.

Is it OK to drive the car over the weekend with the jumper in place till I find a relay?