Starter heat soak?

[Beej '86 325es]

I have an S50 swap, running a starter from a late E30 M20. My starter (although 6 years old) only has 3000 miles on it. It seems to have the exact symptoms of a heat soaked starter.

Is this common on E30's? Even though I have tracked the car a few times, this seems very premature.

[reelizmpro]

What are the symptoms of a heat soaked starter? I have found that it's typically not the starter motor that is problematic but the solenoid.

[Beej '86 325es]

The symptoms are non-cranking starter, only happening when the engine is hot.
I have this issue frequently this year and it's never when the engine is cold. It takes up to 10 attempts to turn the key before it finally cranks...but it always eventually cranks.

[reelizmpro]

Probably the solenoid. That's where my money would be. The solenoid is what activates/engages the starter motor. You can test both while the starter is out with a 12v supply.

[TobyB]

Yes, stupid- common on E36's.
Well, pretty common.

I carry a gallon of water in the trunk-
hot no- start? Water that sucker.
Put the water back in the trunk, start car normally.

Everyone looks at you funny, but then, you're not there anymore, are you?

Usually happens after sitting for 20- 30 minutes after a highway run.

And yes, the solenoid plunger sticks in the bore. So it won't even click.

t

[Beej '86 325es]

Thanks, Barry / Thanks, Toby,

Yeah, it's definitely the solenoid not engaging. Good (I guess) to hear it's common on the M50 motors. I think I'll start out with trying a mylar starter heat wrap.

BTW, I love the water jug trick...that's hilarious! Unfortunately it's not an option when I'm in the pit waiting to get on the track. :)

[whodwho]

I have the same symptoms but will crank if I jump at the diag plug, I believe it to be the ign switch when it is hot out.

Try jumping it at the diag plug, if it starts it will rule out the starter

[jlevie]

Replace the starter with a Bosch factory reman.

[TobyB]

Ok, I'll try the diag. plug. Good idea!

E36 also has a high- current relay in the no- start security box
(ZKE? PDQ? WTF?)

On mine, I get a significant voltage drop as you would as if the solenoid is
TRYING to engage, but can't.

And changing the starter on an E36 really isn't much fun. So I keep putting it off.
I even have the replacement starter...

t

[lukeADE335i]

My m30 swapped car does this too - on hot days after driving the car will not turn over. The trick for me has been to wire a switch for the electric fan so I can manually switch it off & the car will then normally turn over. (With the electric fan running, there just isn't enough juice in the system to overcome the sticky solenoid). Winter driving, it never happens, with a hot or cold engine.


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[Beej '86 325es]

Well it's Spring, so I've got the E30 out and had a chance to test out my new mylar starter wrap. Well, apparently it's not external heat causing the issue, but rather it seems the starter solenoid must be sticking.

For sh*ts and giggles, I tested my crummy Optima battery, and it's only putting out 12.0V. Although I don't think it is the cause of the problem, it probably doesn't help. Even with a weak battery, a starter should at least TRY to crank. I see a new starter in my future...what a PITA on a swapped car.

[lukeADE335i]

I managed to fix mine after close to 3 years of putting up with this. I bought a new starter, and it was still having issues - the switch fix I mentioned above was really just a stop gap.

Check the Black / Yellow (start signal) and the Green / Black (unloader relay) wires to the starter. I had soldered these together and extended them to use an early starter.

Although this was the interwebs recommended approach to using Motronic 1.3 with the early starter, it seems like a bad idea in hindsight.

I cut back and replaced the engine bay part of the Black / Yellow and Green / Black wires in my car, and problem solved. Somehow it was the wires getting heat soaked - causing what for all intents and purposes seems like a poor earth / solenoid issue.

This isn't surprising as the Black / Yellow wire earths the starter solenoid via the start position on the ignition switch to switch it on.

[Beej '86 325es]

Interesting, thanks for the input. When you had trouble starting, would the engine crank at all when you turned the key or just nothing?

Thanks!

EDIT: I just dug into my wiring a bit and found I don't even have the BLK/GRN ground wire run to the starter (unloader relay). I don't have a radio in the car, so I find it hard to believe this is the cause of the issue. If so, it's odd that I haven't had an issue until lately.

[lukeADE335i]

No - the starter wouldn't crank at all when the engine was hot, in hot weather.

Just realised you have an eta - presumably there is just a Black / Yellow (or just plain black) wire to the starter solenoid from the ignition switch.

This wire would be worth checking before shelling out for a new starter.

The Green / Black wire for the unloader relay is only on the late Motronic 1.3 cars.

[Beej '86 325es]

Yeah, I guess you're right. I used a later M20 starter (which has the open terminal) with my S50 swap because it was much lighter than the original 325e starter..

I'm assuming that the BLK/YLW wire is ok, as it's encased in the heat wrap part of the S50 harness and I can't see any signs of damage.

EDIT: Since my battery is only reading 12.0 V, I've decided to start with something I know that needs corrected in the system. I picked up an Odyssey battery yesterday that I'm going to install. If the problem persists, I'll start looking back at the starter again.