1987 Ford F-150 ignition switch

Ok it's not the ignition switch so what else could it be?

Well I taped on the solenoid switch with a wrench and it stops. But some times when I try to start it when I pull the ignition back into the run possition it stops, and other times it won't.

It's brand new, I even took it and had then switch it out for another one and it did the same thing.

Ok I just found out the altinator isn't getting a charge could that be why the solinoid is staying engaged?

I have this same problem. I have tried 3 different relays. The battery is fully charged, the ignition wire to the "S" terminal is going on and off. If I tap the relay, (on the fender), the starter disengages.

Thanks for the reply. As I stated in my post Ihave tested the "S" wire to be sure the switch is functioning properly. I'll check the ground and make sure that the relay is well grounded. That sounds like a possibility.

Finally solved this. After replacing the relay 3 times, checking the switch to make sure power was being turned on and off to the relay, cleaning all the connections, of course being sure the battery was fully charged. I finally removed the starter and took it to Kragens, since it had a lifetime warranty, I had them test it. They insisted it was good. I said to hell with it and bought another starter and relay anyway. Went home and installed them. The truck starts perfectly now. My only guess is that there was something wrong with the old starter, causing it to draw too much power & weld the relay repeatedly. Kagens test seems to be, if it spins, it must be good. This is the second time I have replaced a starter they insisted was good. The first was on my daughter's Mustang. The starter would not stay engaged, but they insisted it was good.

After checking everything, following all of the advice given on this site, un-mounting remounting the starter. Throwing up my hands in disgust & spending $60 on a new starter when there was nothing other than my gut instinct to tell me it was the problem, The truck starts, and the starter disengages when I release the key. I do not think you should be so fast to discount the starter as being the problem.

The test method does not place any load on the starter, its not turning anything. I'm sorry but you will not be able to convince me that the starter was not the problem all along.

What I was saying was neither of these conditions existed. I had removed & reinstalled the starter, even though it had been working fine for a year or 2 before the initial problem. I checked to be sure there was not a lose bolt or something causing it to be improperly aligned. The starter was not jammed mechanically. I charged the battery fully before attempting to restart it after the second relay install. The third relay included being sure the relay was well grounded.

It's fixed now, and I'm happy. Thank you for all of your help.

My point being don't discount the possibility that the starter may be bad, even though it turns over the truck.