Won’t try to start when hot, after long drive

[mcgee]

Yesterday (and right now) I turn the key and no start. Nothing. All power there but no effort from starter.

Yesterday I wiggles a lot of things, shifted up and down, twisted keys a bunch. Finally started. No more problems from OR to SF.

Now it’s doing it again.

Is the solution waiting?
What is the cause?

[Bimmerod]

I would tap on the starter solenoid. I had this issue and a little tap helps it get in the right position. Not too hard to reach with an extension or long metal bar. You may have just gotten lucky with the keys etc. Since it's a intermittent issue, I would check there.

Bimmerod


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[OLD MAN]

Steve - SAY IT IS NOT TRUE!!!!!

What Bimmerod said can be true - yours is all new. I remember this in my dreams.

So things in the starter get hot - they draw more amps to do the same job.

With "Our E21's" hot days - hot starters can show us an issue with warn/aging ignition switch, the contact that is hit when the key is in the "START" position. This is the one that sends power to the solenoid to power the magnet setting everything into motion. Hot magnet slide has more friction needing more amps to move.

What I use to do with our 65 chevy Malibu wagon when this happened was pour water on the starter to cool it down. Small block chevys are really bad with this issue.

Running a wire from the solenoid to a push on push button on the dash with the other side connected to a hot wire when ignition is on is an easy way to this the ignition switch and have a quite fix till you decide to tackle an ignition switch change.

[320iAman]

Its the No 50 wire from ignition switch to start solenoid, with the ignition switch turned too the start position there should be 12 Volts on the Black wire No 50 wire to trip the start solenoid on and get the starter motor turning. I'm up too the Big 7 upgrade on the Car electrical system to rid it of starter, alternator, battery issues, Big 7 upgrade has lifted the voltage and amperage from bumper to bumper, I'm not done with the electrical system either, there is plenty more upgrades.

Randy

[mcgee]

Yeah, Old Man. Starter problems... still??? Now I can sweat instead of freeze while messing with it... Ha ha.

I didn't try tapping the solonoid since it's new. Thought it might be the auto trans alignment problem. Shifted a bit again and it started, about a minute after this post. But again, it could be just the amount of time I spent waiting, and all my rigamarole had no impact. Maybe just cooled off. Next time I'll give it a tap immediately and see if that's it.

Thanks, guys.

[epmedia]

In addition to the other comments, at least first make sure the smaller (red and black) wires are clean and snug on their battery terminals. Of course same for both main battery terminals and posts as well.

Also, sometimes the terminal (50, as Randy mentions) can loosen. Unplug it, maybe it's a loose fit. If a loose fit, tighten the spade connection on the wire end.

Alternatively, you can add a piece of wire to that terminal 50 for t-shooting or (worst case) getting stranded purposes, ie: remote start purposes in case it is ignition switch related.

wait a sec... is it an auto transmission?

[OLD MAN]

That is correct with the auto there is the whole natural safety switch issue.

Can they cause issues "only when the car is hot?"

[320iAman]

Starter Relay as well.

Randy

[DougIng]

I’ve had this issue too. But I’m on a E30 M20 swap with DME so I can jump two pins in the diagnostic connector and it will start right up! All but rules out the starter. If a fix can’t happen right away consider what Old Man said and have a jumper wire/button at the ready.

[OLD MAN]

I'm up too the Big 7 upgrade on the Car electrical system to rid it of starter, alternator, battery issues, Big 7 upgrade has lifted the voltage and amperage from bumper to bumper, I'm not done with the electrical system either, there is plenty more upgrades.

Randy

OK Randy I have never heard of the "big 7" up grade. I may have done some of them without knowing they fell under a label.

Can you list them - or link to them for me?

Thanks.

[320iAman]

First, I have qualify No 50 wire from ignition switch to start solenoid, this is the wiring for non start relay models,, manual transmission models,, automatic transmission models with the start relay the ignition switch in the start position there should be 12 volts at the starter solenoid wire, yet the ignition switch in the start position would signal the starter relay and get it too close and thence the output would go to wire #50 or thru the wire with the female spade connector (6.2mm size) thru the male spade terminal on the start solenoid to get the starter motor turning.

Big 7 wires

1.) Battery + post to start solenoid awg 1 on up
2.) Battery + plus to alternator B+ awg 4
3.) Junction Box or Fuse Box Red wire to Battery + post awg 8
4.) Battery - Post to Engine Ground awg 1 on up
5.) Battery- Post to battery box(chassis ground) awg 1 on up
6.) Alternator B- to Engine ground awg 4
7.) Chassis Ground to Engine Ground awg 1 on up

All these wires are ofc-oxygen free copper wire, stranded, have terminal lugs on the ends -crimped and have adhesive heat shrink(marine grade) to seal the stranded wire insulation to the lugs to keep air, oil,water, moisture ,ect out from the wires ends into the contact zone inside the lugs, ridding of shorts and other undesirable effects.

The Wire should have imprinted on it OFC else most likely copper clad aluminum not as good as ofc.

Like I said I 'm not done with electrical upgrades over stock factory wiring gauge , ect.



Randy

[mcgee]

That's a good list.

I re-wired a 6.2L to fit into a small block Chevy van and learned a lot from that. Good wires matter.

[autox320]

First, I have qualify No 50 wire from ignition switch to start solenoid, this is the wiring for non start relay models,, manual transmission models,, automatic transmission models with the start relay the ignition switch in the start position there should be 12 volts at the starter solenoid wire, yet the ignition switch in the start position would signal the starter relay and get it too close and thence the output would go to wire #50 or thru the wire with the female spade connector (6.2mm size) thru the male spade terminal on the start solenoid to get the starter motor turning.

Big 7 wires

1.) Battery + post to start solenoid awg 1 on up
2.) Battery + plus to alternator B+ awg 4
3.) Junction Box or Fuse Box Red wire to Battery + post awg 8
4.) Battery - Post to Engine Ground awg 1 on up
5.) Battery- Post to battery box(chassis ground) awg 1 on up
6.) Alternator B- to Engine ground awg 4
7.) Chassis Ground to Engine Ground awg 1 on up

All these wires are ofc-oxygen free copper wire, stranded, have terminal lugs on the ends -crimped and have adhesive heat shrink(marine grade) to seal the stranded wire insulation to the lugs to keep air, oil,water, moisture ,ect out from the wires ends into the contact zone inside the lugs, ridding of shorts and other undesirable effects.

The Wire should have imprinted on it OFC else most likely copper clad aluminum not as good as ofc.

Like I said I 'm not done with electrical upgrades over stock factory wiring gauge , ect.



Randy

Good list Randy. In the audio world it's big three. Battery to alternator +, Battery to frame -, Alternator to frame -

Another one to add is good ground from back of the head or valve cover to the frame/body. Helps the ignition for easy path with spark plugs ground electrode not having to travel through the headbolts and block.

When we rewired the entire car for race use made sure to put #6 for the mains and #10 for any additional grounds. With three main ground points using bus bars to give direct link to the battery and not relying on the TIN WORM chassis Keep it simple. When in doubt direct path is best to the battery. These older cars can have serious degraded ground points causing electrical issues. Especially the fuel pump voltage drop from the path it takes to get power.


New starter and tapping the solenoid already LOL say it ain't so. They warn this is harmful but they also know the issue

New M3 starter out da box

[320iAman]

Additions and improvements are always welcome. BMW Stock wiring( 16 cables or so vs several 100's and more stranded wire conductors) Battery Post is AWG 4 to starter , Ampacity is 135 amps, maximum transmission power is 60 amps, starter draw according to haynes is 275 amps. AWG 1 up is double in Conductors cross section diam( when awg 4 stranded-which it is not), and 1/2 the ohms resistance per 1000 ft. When I considered this I seen right away why my starter was sluggish,, upgraded the wires--the stock starter turns very fast- no more sluggish starter getting overheated. I have a M5 Starter as well new in the box, I read Lances post on compatible starters for M10, researched further and found inexpensive new, warrantied M5 Starter -fits without the bracket, faster spin up, most power and draws less amps than stock one , M5 starter is from certain years only !...

Terminal Lugs I used were tinned copper and bare copper( fuse box bus bar to + Batt post)


Randy