I have done the searches and not run into this: I have an '87 S4 auto with a new battery. It starts great when cold and runs great. It only has about 40K miles. Here is the problem. Twice in the last week, when hot (driven 30 minutes or so), it would not start and would not crank at all when I tried to start it after it sat (even up to an hour or so). The dash lights, came on, but there was absolutely no sound from the starter. What I have noticed is this: Both times I fiddled with the remote battery post cover, i.e. unscrewed it then screwed it back on, the car started right up. Any ideas on what's going on and what a possible fix might be? Thanks?

 

New ground strap or new starter.

 

Actually, let me ask, when you tried to start and there was nothing from the starter, did the dash lights light up?

 

Since you seem to be gone already I'll tell you my thinking...

If the dash light are out when you try to start, that means the whole car isn't getting juice. Likely cause is the ground strap. When you fiddel around with it, it makes a connection and starts.

If, however the lights are on, it's likely the starter is failing and needs to be replaced. (that's what happened on my car.)

 

Have you checked the 14 pin? it is up by the jump post and in removing the jump post cover you may have jostled the 14 pin just enough to aid contact. I'd check both the pins on the 14 pin connector as well as pop the covers off to verify the wires are stil connected well to the individual terminals.

 

With respect, even if the lights are on it could still be a ground strap. Sometimes they degrade and the starter puts the most load on it. Does the ground strap at the back of the car get warm after trying to start the car?

 

The dash lights do come on. The connections under the remote post cover look fine. If it was the ground strap, would/could screwing on unscrewing the remote post cover make a difference? I will check the ground strap in the back to make sure it is tight and clean.

 

Sometimes the ground strap will corrode inside and you can't see it. There was a thread by Tampa928s recently where he had this problem, although he didn't have interior lights ( as Andrew mentioned ). I'll try to dig it up.

Edit: Here it is

 

first diconnect the battery then remove the hot post and clean these wires then open the 14 pin connector above the hot post and inspect the pins for corrosion you can use a pencil eraser to clean off all of the elex contacts. After this go to the battery and clean every connection there on the + and the - sides also clean the ground strap where it meets the chassis.
If still having problems then replace the starter relay with the horn relay./
Inspect the starter relay base for melted connections and smell it for burning,
open it if you find either condition as it may be on its way out

 

Also inspect and release crank end play, and measure!