Need to Disconnect battery for a few seconds to start...

Tried searching the interweb for this issue but couldn't find anything. If this is covered in another thread please point me in the right direction.

Car: 1995 E36 M3 with ~130K miles.

The Issue:

Randomly and occasionally (sometimes twice in one day and then weeks without the issue) I turn the key to start the car and it loses all power instantly. No noise, just a small sound like turning the car off from key position 2. The car in this state is now dead to the world: No lights, windows, door locks or window drop (that 1/4inch thing when you open the door on a coupe). I disconnect the battery for about five to 10 seconds and then reconnect the battery and try again and she fires right up strongly like nothing was ever wrong.

Notes: This seems to happen regardless of if the car has been sitting for a day or so or just driven for an hour. So each time I go to start the car it's a bit of a crap shoot. The battery reset trick has worked every time so far.

My thoughts are one or both of the following:
1) Bad ground somewhere shorting out the computer
2) Relay going bad and becoming flaky

Thoughts? Ideas to diagnose? Although I have a good shop in town that works on my car I am hesitant to take them an issue that is so sporadic. If I can find a way to replicate it reliably I'd have something to take them or could fix it myself if it's shade tree mechanic doable.

Thanks!
James.

This is really odd. I'd suggest reposting in the regular e36 section.

Originally Posted by petriej

This is really odd. I'd suggest reposting in the regular e36 section.

Thanks petriej. I searched the E36 forum and found a couple people with similar issues and they were pointed to check the chassis grounds. I'll check on that before I repost.

James.

I've had the same problem on many cars of mine, for me it was always the battery terminals (on the battery or on the car) and the fix was a good cleaning. (baking soda and water works for me)

Good luck,
Nick

I can just about promise you your problem is a loose connection at your battery terminals. Sometimes you can just clean and tighten them really well, but other times they may be cracked or worn badly enough that they can't be tightened sufficiently enough to make a proper connection. Try cleaning and tightening them with proper tools of course, and if that dosn't work just replace them.