94 530i won't crank

[ptrop]

I have a 94 530i with 78,000 miles. My daughter was waiting for about 30 minutes with the car idling when the radio died and then the car died. After that, the car would not crank. From her description I thought maybe the alternator went out or serpentine belt broke and she had been running on battery power until it gave out. I had the car towed to my work so I could check it out. Belt was fine, all electrical was working but the car will not turn over. Used jumper cables to charge the battery from another car but still nothing. I thought that maybe the antitheft code got activated and went through the procedure to deactivate it by disconnecting the battery for 5 minutes and then waiting 15 minutes with the key in position 1. Still nothing.
Does anyone have any words of wisdom?
I've read something about an immobilizer relay??? Is this real? If so, where is it and how do you check it?
Thanks.

[BillionPa]

crank position sensor or dme relay, maybe the fuel pump finally died?

[pingu]

My "former" problem (that I thought was fixed) with the car not cranking when hot has come back again... so I'm interested in this thread.

BillionPa: how would the crank position sensor (CPS) or fuel pump stop the car from cranking over? I can see how a faulty CPS would inhibit the ignition system, and I can see how a duff fuel pump would mean there's no fuel to ignite, but how do they affect the starter motor?

[joshua43214]

Normaly I would not ask this first , but since it was a young driver I will ask it now.

Any chance the engine overheated or the oil leaked out and she did not notice? make sure the engine is not locked up.

Aside from that. verify that you have power on the big wire to the starter, and to the small wire when you crank(disconnect to test), if you have both, either the engine has no ground(not as likely) or the starter is fried. It would not hurt to jumper a remote wire to the small wire at the starter and see if it will crank that way, this will eliminate the ignition switch and assorted parts as the culprit.

[ptrop]

Thanks. I know what you mean. I did check oil and coolant and all is normal.
I'll check the starter this afternoon.

[yaofeng]

Interesting. I thought this only happens to my SAAB but BMW has this also. But the E34 has the battery under the rear seat do corrosion of the battery post connection should not be an issue. But make sure they are tight.

Trickle charge the battery up.

The starting circuit is dead simple. On it are the battery, the ignition switch and the starter. Start looking for loose connections first.

[BillionPa]

oops, as you can see my post was last yesterday and for some reason i read "will not crank" as "cranks but doesnt start"

if the starter motor siezed it could stop the engine dead in its tracks and not let it start up again, thats the only one thing i can think of that both problems have in common. the DME relay would still let it start, the starter relay wouldnt kill the car when its running....

as i write this, if the alternator had crapped out, and it killed the battery, it would stop and not start again, so it could be that.

I would remove the main drive belt, and check the water pump, power steering pump, ac compressor, and alternator pullys to see if they move. hopefully they all do.

[ptrop]

Finally got a chance to get under the car and check if power was going to the starter. Power good. R&R starter. Hooray.
This whole thing was a little strange to me as there was no hint of the starter going bad. Usually there is a drag or spin. This just went dead. Not even a click when turning the ignition. Live and Learn. Thanks for all the hints and advice.