No start after speaker change

[Voices]

Just picked up my first E34 a week ago so pardon my stupidity. A few days ago I tried swapping the rear driver side speaker and after plugging in the new one the car wouldnt start. I reconnected the old speaker and it still didnt start. I let it sit overnight and the next morning it started on the second try and worked for a few days til this morning when it wouldnt start again. I didnt unplug the battery when I did it and I know I shouldve. The car doesnt crank or anything I turn the key and nothing happens. The lights and radio and other electronics work but I havent tested the battery yet. Any other ideas what it could be.

[Voices]

Little update got the backseat removed to test battery and it was at 12.08 volts sitting. Had someone try starting the car and it dropped to 11.82 volts when trying to crank. After a bit I got the car to start and tested it while it was running and it sat at 11.9 while running. I checked it after it had been running for 5 min and dropped to 11.86 so I think its an alternator and the speaker thing was just a coincidence

[demetk]

First take a look at the voltage regulator to see if the brushes are worn down.

[Voices]

Little update here the alternator was swapped a second time car is still having issues. The battery is good had it tested and swapped the starter relay and fuses were checked so looking for ideas

[E34 Lives]

I once had a no start situation like your. You should double check fuses, especially the ones for the fuel sending system. If it is the original fuses with the thin wire, they can develop hair Line break and you can only see in bright conditions. Check or even replace if it is those original fuses …. I had the fuel pump fuse develop a hair line break and would intermittent not start. I found the problem only after replacing new pump.

I also once had a short in my heated seats that cause no start, that was a really hard to troubleshoot. Decided to take it to the dealer and they traced the short to the seat heaters and was a quickly fix.

[E34Driv3r]

What year is it? Does it have an immobiliser?

If it's still not starting, try putting it onto key position 2 and stick a jumper across the starter relay to see if it cranks. The key switch themselves can give trouble in these too.

If it's cranking but not starting then it could be a fuel supply issue. The fuel pump might be past it, or the filter might need changing. The fuel lines themselves are prone to rusting in colder/wetter climates too so that could be an issue.

Your battery voltage is definitely too low. I'd stick a multimeter on there and start pulling fuses one at the time to look for fluctuations to see if you have a parasitic drain. Also, try hooking the car up to another car with jumper cables and see if it starts reliably.