Last week my "89" 5.0 manual trans. mustang wouldn’t start,I called the tow truck and that was that. I was told thejunction box on the side of the firewall where the batterycables hook up was bad. So I replaced it and the battery. The car started! Moments latter,the wife and I were on our way to wholly world to pick up a few things... On the way their I decided to cut the car off while on the HWY and restart it just to see if the alternator was working.... Nope I had to crank the car while on the HWY at 80 mph. We pull into the Wal-Mart parking lot, I turn the car off, and the car’s belts kept running. I had to disconnect the batt. To cut the cars belts off... While reconnecting the batt. cables the post sparked as if the batt was backwards. Driving the car home was a nightmare, once again, Icalled the tow truck because the car quit on us!The starter went bad, so I have replaced it and still I’m having problems... Any Ideas?

 

The belts are not turning by themselves.
Your starter solenoid is located on the left
fender. I would suspect that the starter is
being kept running by a short up there.

The sparking is normal if the starter is drawing
current. Did you hear it turning?
The solenoid is cheap compaired to the
price of a starter.