starter keeps going, and going

[aposak]

I was cranking the truck the other day, trying to get it to start (it hasn't wanted to run lately). After about 30 seconds of cranking, I let the key return to ON from START. Still cranking. Turned the key all the way to OFF. Still cranking. Pulled the key out of the ignition. Still cranking. As the batteries were starting to die, I finally got the positive off the battery. The marine terminals with thumb screws really helped.
Tried it again later, after everything had cooled and the batteries had charged. When I bumped the starter momentarily, it would stop cranking when the key turned back. When I cranked it for a few seconds, it would continue to crank over after I turned it off.
Initial thought is the starter solenoid. However, there's one on the fender and one on the starter. Which one should I go after first? I replaced the ignition cylinder about a year ago because the ears were broken off, and the starter this spring because it was weak. Just before this happened, I added a line from the fender-mount starter solenoid to the oil pressure switch for the electric fuel (from Tim's I/C page). This line is only to activate the fuel pump relay during cranking, not to actually run the pump; shouldn't be a large current draw.

[speeddemon31176]

See which one is really hot after cranking for a few seconds and there is your culprit. It would be impossible to guess as to which one but as a guess I would say probably the fender mount first(cheaper). Then I would look at the starter.

[aposak]

Thanks for the suggestions. I tried swapping the fender solenoid with a new one, and the starter solenoid with the one from my old starter. Neither seemed to help.
After that, I did some more testing with the switched output from the fender solenoid. It only has 2 wires: the one to the fuel pump relay, and the one to the starter solenoid. If I left only the fuel pump relay connected, it behaved properly. When I turned the key to START, the fuel pump would cut on, and cut off when I let off the key. When I put only the starter on the solenoid, it still kept cranking after I let off the key, and even after the truck was running. However, when I set it back up to the fuel pump only on the solenoid, then touched the starter lead to the always hot side of the solenoid, it fired up properly. Those tests seem to be taking me in different directions as to what is wrong. I also tried pulling the ignition switch wire (small terminal, with the boot) off during one of the runaway crank times, but that didn't stop the cranking. Didn't think to check it with the fuel pump only, to see if that would actually work, but I will tonight.
Any thoughts on what could be wrong, or additional tests I can do? I'm trying to avoid dropping another $200 on a starter, since I already dropped that much on a new one this spring.

[speeddemon31176]

You may have a defective ignition switch on the steering column. Not the key cylinder either. It is located under the dash on the column. Look and see if it has melted connections etc. and replace whatever is damaged. Ford has had problems with them for years. It is the only other thing I can think of in the system that could cause it short of a bad starter.

[dieselcamino]

my plastic shroud has stuck before on my ignition switch, after a dissasemble and a clean out it works smooth now