My son is driving an 88 740 GL non-turbo. The car has developed this tendecny not to start (it seems always when it is least convenient).

Here are the symptoms.
When you turn the key, the lights turn on but the start does absolutely nothing. No Click/Nothing. We have tried starting in neutral, moving the shifter slightly to see if it woudl enable the car to start. Nothing obvious.
THe only thing that seems to work is waiting 30-60 minutes and the car starts as if there wasn't a problem.

This happens once every couple of weeks.

Based on other threads I thought that it might be the starter inhibitor switch. So this morning we removed it and checked the wiring and harness. Using an ohm meter, I checked that the Park and Neutral positions were correctly being identified. Seemed to be fine.

Althought it really wasn't very dirty, I cleaned it up and we reinstalled it. Since I relly didn't do anything, I am pretty convinced that the problem will reoccur.

MY brother (previous ower) indicated that he had seem this before and repalcing the battery made the problem go away for more than 2 years.

I am not sure why the battery would play in this. My thought is that this is a red herring.

Any ideas what we should look at?

 

Do the lights dim while you are cranking it? You may try giving the starter a "whack"... Problem could be the starter or the ignition switch itself.

 

In this case the starter make no attempt to crank and the lights don't dim when you turn the key.
I had AAA test the battery and it tested fine.

I have tried tapping the starter and that doesn't seem to work either.

As far as symptoms it does seem to correlate with the starter inhibitor switch not working but as I indicated it seems to check out ok.