DukeOfUndersteer UltimaDork
4/15/20 7:53 p.m.

Back story: 86 E30 "E" with a M52 swapped in. Has an automatic engine harness even though it's a manual swap. Lay the harness in, plug in all the connectors, connect the battery, check the power slug for 12v, then go to attach the engine harness power supply to the slug. As soon as I make contact, there is instant power to the starter solenoid. To add to the background, I had accidently smashed the ignition tumbler while removing the dash and I do not have the ECU plugged in to the harness at all. I've checked all my grounds, double checked all the wiring and harness. Where did I go wrong?

Curtis73 (Forum Supporter)
Curtis73 (Forum Supporter) MegaDork
4/15/20 8:50 p.m.

Without 6 hours and a wiring diagram, all I can offer is this:

E30s route the starter solenoid (either power or ground, I forget) through the NSS on the automatic.  It goes through the clutch on the manual.  Possibly without the NSS in the circuit, things are cranking without the key?

z31maniac MegaDork
4/16/20 7:37 a.m.

Time to get on R3Vlimited and look for the pinout diagrams and compare.

I'm no help on the older cars, my swap was a "late" E30. The bulkhead connector pinout changed in '87 and I believe was different between e and i cars anyway.

iansane (Forum Supporter)
iansane (Forum Supporter) New Reader
4/16/20 10:54 a.m.

Aren't there two sets of wires going through the starter? (not counting the battery cable itself) One on each small post? I vaguely remember having a weird power issue with that when doing my swap. That and the fact that many of the brown ground wires look like faded red power wires; I'd check to make sure they're all correctly powered/grounded. Good luck.

DukeOfUndersteer UltimaDork
4/16/20 11:45 a.m.

In reply to iansane (Forum Supporter) :

Yes, you are correct, and no, I am missing one small wire. I think that's where my problem lies at the moment. I have the two big wires: one from the harness and one from the alternator. Then I only have one small red wire going to the top small post on the solenoid. I have to locate the second small wire that goes to the second small post on the solenoid.

iansane (Forum Supporter)
iansane (Forum Supporter) New Reader
4/16/20 12:56 p.m.

IIRC, one post transmits power on crank to the electrics (to kill power to all the ancillary accessories) and one posts is what kicks the solenoid out. Maybe the wire you have hooked up goes to the other post and you still need to find the solenoid engage wire? 

DukeOfUndersteer UltimaDork
4/16/20 3:19 p.m.

So, by looking at the wiring schematics, the starter has the one big post for the 12v from the battery and alternator, then one small post for the ignition switch, and one from the starter relay. I believe I have the starter relay wire, so I am missing the ignition switch wire. How does it still have power though? It's like the relay is stuck open 

DukeOfUndersteer UltimaDork
4/30/20 4:16 p.m.

Okay, time to update this:


I found in my voyages of the interstate super highways, that I had two wires that went to the starter that were missing from my harness. They were actually cut by whoever got it from the junkyard, so i was able to extend them and solder/heat shrink everything. To continue my wiring search, I was missing the "exciter" wire that goes from the alternator to the ECU. I have found that, but here is where i go wrong. 

In the wiring diagrams, I have been looking at, there are two wires: the exciter wire and another wire that goes to the cluster for the battery light. I have the original connector on my harness and do a continuity check that pin blah blah on the round connector is the alternator exciter and pin blah blah on the big round connector is the battery light wire. The car I was able to get the exciter wire off of did not have a connector. It went directly to the ECU. So it was missing the other wire that goes to the battery light on the cluster. Do i just cut the connector off and solder/heat shrink the exciter wire on and not worry about the battery cluster light?

If this is difficult to read or understand, I can try and supply pics and give more background on the situation

Slippery (Forum Supporter)
Slippery (Forum Supporter) UltraDork
4/30/20 4:27 p.m.

The one that goes to the cluster controls something with the alternator. I know this is vague, but if you have no cluster, the battery does not get charged. 

Not sure how or if this even helps you lol. 

DukeOfUndersteer UltimaDork
5/1/20 9:24 a.m.

In reply to Slippery (Forum Supporter) :

That's what i was scared of. Is it possible that i might have thr wrong alternator on my car? I don't have any plugs on it, just the main alternator wire and exciter slug

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