I have an '86 F250 with a 460. I just had the engine replaced about a month ago. I drive it daily. About one week ago, it started losing all spark - only for an instant. It would only do it once or twice just after starting to drive. At first, I thought it was just cold. Then I noticed that my tachometer dropped to zero when it happened. One day on the way home from work, it started doing it off and on and off and on and off. It finally just died. I was able to get it started and get it home. Since then, nothing. I replaced the ignition control module - nothing. I replaced the coil - nothing. The distributor was replaced with the engine, so it is brand new. I did check all the wiring and it seems OK. I lifted the distributor cap and had my wife crank it over. It was turning fine. Then, I held the coil wire to the distributor with a rubber wrapped pair of pliers. When I had my wife crank it again, there was no spark from the wire to the top of the center post on the distributor. As soon as she let go of the key, I noticed a spark, and got a little shock. I had her do it again to verify this. Sure enough, just as she let go of the key, the truck tried to fire, a spark shot across the gap between the wire and the distributor post, and I got a nice little shock through the rubber wrapped pliers. So, I replaced the ignition switch on the steering column - still nothing.

I'm much smarter about cheap rubber wrapped pliers, and about my steering column. But, I'm no closer to starting my truck.

Can someone please offer some ideas?

Thanks,

Skimmer

 

What if it had something to do with the voltage on the wires connected to the ignition switch. I'm just thinking out loud, kind of. But as your wife is letting go of the switch, it might be completing the accessory circuit and the engine would still be turning which might call for a spark. Once again maybe there is a way to defeat the ignition switch just to totally eliminate the wires or connections.

 

try an ignition module

 

I noticed you said you replaced it but, this is a clue when it fires as you let off. 99 times out of 100 its a bad module. Take it off and have it tested and while you're there check out the wiring right there where it plugs in.

 

Thanks, I will try these ideas. I had not considered that I may have got a bad ignition module.

 

have a ongoing simular problem...my 85 F150 straight six cuts out or fails to start right away. Nothing happens (fires) while cranking till you actualy let the key go - then bang - she fires and starts right up. Did you find out why yet? Did you replace the IGN MOD? Mine is a DURASPARK II .