Have you guys ever heard the term, "back-feeding." This is the deal. After running the car for a little while (10-15+ minutes), I turn the ignition off, but the engine remains on, except it sounds like an extremely rough idle. Well, the guy I bought this car from set up a fan relay to the ON switch at the key. So the fan is on all the time. My mechanic told me that was the prob. He showed me by disconnecting the fan. The car automatically went dead. ??? I am baffled. Any ideas? I am getting really pissed at having to put it in 1st and choking it to turn it off..Thanks guys..

 

It sounds like it's dieseling- running on without any spark. this is caused by the idle being too high, or by it being too far advanced. If the starter seems to labour when you try to start the engine hot, it's too far advanced.

 

Backfeeding is exactly what that is.

What happens is that the electric fan is running while the car is on. The fan wire is most likely being powered from the same wire that the ignition is powered from. When the car is shut off, the fan keeps spinning from inertia and is now acting like a generator, feeding power into the ignition wire. The motor will keep running (crappy but nonetheless) until the fan stops spinning.

You can solve that problem by powering the fan from the battery with a relay, or installing a diode on the fan's power wire so that it won't "power" the ignition anymore. Basically isolate the fan's power system from the ignition's power system. I would do the former.

 

Thanks alot guys...great help. I'm going to try and get that done this weekend.

 

JZA is right on the money, seen it many times

 

Hey place the diode on the ALT plug marked 1 with the line facing the ALt. I had the same problem once I place the diode the car operated properly off and on Diode # 276-1661 Radio Shack for $3.00 for 5