1981 BMW E21

>1981 BMW E21
>randomly won't start
>turn key, buzzer sounds, dash lights light up, but starter doesn't turn at all
>been relying on jump starts
>got a new battery, problem persists
>checked alternator, charging fine
>took it to two different mechanics, one specializing in European cars and the other in electrical systems
>neither could find any problem; ignition switch and starter seemed normal, ditto for alternator
>when they tested, it would start up every time

And I mean randomly. I once drove 40 miles, parked to get food, come back, won't start. But after a jump start it'll work a few more times, then won't start again. What the hell's going on here?

>a bmw with electrical issues
SHOCKING!!!!

Does it click it all? Starter contacts? Hard to say, on a car that old any of the electricals can be bad.
Nice meme you retard.

See you shoulda bought that Reliable Corolla

Except it isn't shocking then, now is it.

No sound whatsoever.

shit nigga that's bad
You most likely have either some sort of parasitic drain in your system or something is intermittently making contact.
When the car won't start and you have to jump it, is the battery actually dead? I would get a multimeter and check the voltage on the battery next time it happens.

>What the hell's going on here?
Bad ground somewhere.

If an electrical systems mechanic can't fix it out he must be fucking stupid. Get a multimeter and start tracking voltage from the starter. If the starter gets 12v and it still doesn't start there's you're problem. If it isn't getting voltage start tracking backwards to the ignition switch and main power. Also check for resistance, some cars have a ground strap for the trans/engine and they can get pretty fucked over 35 years.

relay

This. It sounds like something is shorting out and not sending power to the starter, so check the engine grounds. Sand them down and tighten them. All of them.

No solenoid click means zero voltage is getting to the starter when it happens, so there's a start.

>neutral safety switch?
>starter solenoid?
those would be my guess
having same problem on my 560SEL 1987

OP, clean all electrical connections, then check if the hardware is functioning or not.

>source: EE degree + maintain electromechanical systems professionally.

Unless there's a bad connection at the solenoid. All the starters I had there was an exposed strap from POS on the solenoid to POS from the battery. But I wouldn't be surprised if it was a trans ground strap hanging on by a thread. Every time the eninge/trans shake in the mounts it could be disrupting continuity.

starter solenoid relay / main relay / main electrical / whatever tells the PCM to send voltage to the starter

>bmw

>meme

>corolla

>is the best car ever

bad/loose ground. check all the grounds. i promise ones rotted, loose or disconnected

I had the same problem with my e30 for a while. What I did was get a multi meter and check for parasitic draw. while you're doing this you're going to check all fuses anyways. I had a draw for interior lights/radio/dash. And to add to that I cleaned all my grounds. That fixed my constantly needing a jump start, but then mine would start intermittently. I then found out there's a neutral switch in autos and something else for manuals idr but the connection on that was loose. now I messed with those connections found by shifter, and it starts everytime.