Hello, Need a bit of help... 1991 348 I had the battery disconnected while I was doing some other work (fixing a fuel leak, changing gear oil etc, not electrical work); when I reconnected, the lights all come on the dash and seem to have power, but the car will not turn over, no click click, nothing. I took the battery out of the car, charged it overnight, replaced the old connectors, had it voltage and load tested at the battery shop in town, same result.
The three main causes of what you are experiencing are: 1. starter relay issue (not enough voltage through the wires to it or a dead relay) 2. ignition switch wiring issue 3. Battery isn't delivering adequate voltage/current for whatever reason (corroded terminals, failed internal cell, etc.).
Well, I think it is fixed; may have been that the positive terminal connector wasn't tight enough. Followed the steps in this and another thread (re: replace starter), checked the bullet connectors, traced the voltage to the starter, jumped the starter etc. Everything looked good and saw the same voltage at the starter, and shorted the starter etc. Went back and tightened everything and she fired right up! Thanks for the assistance once again, my Sunday just got a lot better!