It sounds like you have a problem inside the column. The ignition has a gear on the end of it that pulls back a rod that shuts the car off, not sure what exactly it is called though. I had a similar problem in my chevelle and found that the gear on the end of the lock cylinder was stripped. You will have to remove the lock plate to get to it, the easiest way is to use the correct puller. I was lazy and had a wheel that was f.u.b.a.r. and was able to wedge a small screwdriver in there to apply pressure on the rod enough to catch the gear and turn the car off, but eventually replaced it. Odd enough I found the gear at my local dealership. Good luck!
if you are using the factory wiring it can also happen if the starter solenoid shorts, or if the battery cable is touching the outer small "R" stud on the solenoid. Somehow you are still getting 12v to the coil with the key off, and if you are still using the factory bypass wire it could be coming from there.
f.y.i. i have hei. i will check out the battery cable tommorow. I know that i am getting that bar pulled completely back because i checked it already by pulling the ign. switch and looking and testing it.
I agree with the Diode thing. It sound complicated at first, but its really not. I put a M.A.D. Electrical system in my 68' and could'nt be happier. The Diode I installed went on the 12v turn on wire on the alternator( #1 ). The instructions said that it acted like a one way check valve for the ignition. Somthing about after you turning the key off, the 12v turn on wire backfeeds the ignition and supplies voltage to the coil instead of the keyed source. So basically the alternator keeps the engine runing.
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