Attention: TDR Forum Junkies 
I got done with school on Thursday, went to start my truck, and the starter engaged and didn't stop!!! It just kept cranking, the engine didn't start, and I was panicking. I cycled the key thinking that the solenoid was stuck, but no luck. It just kept cranking. Finally, after about 5 or 6 seconds (seemed like 5 minutes, with visions of my truck catching on fire and burning down), I let my foot off the brake (I'll explain in a minute) and it stopped. 
Oo. Oo.
After I dried my pants a bit, I proceeded to call everyone I knew that knows anything about these trucks (thanks to Bill and Ken Jones!) and started to diagnose the problem. Ken mentioned the relays on the firewall behind the pump, and I noticed that one had nothing plugged into it (it never has by the look of the corrosion on the terminals) and the other was lying on the master cylinder upside down, hanging by the wires. I disconnected it and it turns out to be full of green muck. I had just gone through a car wash at a gas station the day before that sprayed a powerful stream of water right down the cowl. The soap must have gotten into the relay and corroded it. That relay happens to be the one that powers the pull-up coil in the shutoff solenoid. The relay gets triggered by the starter, and pulls up the arm, and when the starter disengages, then the smaller hold-up coil in the solenoid holds the arm up to keep it running. Apparently the faulty relay sent a feedback current to the solenoid on the starter to keep it running until its power was cut. I have a relay in line with the starter solenoid trigger wire that is powered by the brake light switch for security, so when I let off the brake, that relay cut the power to the starter solenoid. Wheeew!! Good thing it stopped!
So it didn't start because the pull up coil never cycled, and kept cranking because that relay somehow kept the starter on.
I replaced the relay today and everything is fine. Thought I would pass this along because it is a weird problem, and could be very confusing to diagnose (I know).
Chris
Oo. Oo. After I dried my pants a bit, I proceeded to call everyone I knew that knows anything about these trucks (thanks to Bill and Ken Jones!) and started to diagnose the problem. Ken mentioned the relays on the firewall behind the pump, and I noticed that one had nothing plugged into it (it never has by the look of the corrosion on the terminals) and the other was lying on the master cylinder upside down, hanging by the wires. I disconnected it and it turns out to be full of green muck. I had just gone through a car wash at a gas station the day before that sprayed a powerful stream of water right down the cowl. The soap must have gotten into the relay and corroded it. That relay happens to be the one that powers the pull-up coil in the shutoff solenoid. The relay gets triggered by the starter, and pulls up the arm, and when the starter disengages, then the smaller hold-up coil in the solenoid holds the arm up to keep it running. Apparently the faulty relay sent a feedback current to the solenoid on the starter to keep it running until its power was cut. I have a relay in line with the starter solenoid trigger wire that is powered by the brake light switch for security, so when I let off the brake, that relay cut the power to the starter solenoid. Wheeew!! Good thing it stopped!
So it didn't start because the pull up coil never cycled, and kept cranking because that relay somehow kept the starter on.
I replaced the relay today and everything is fine. Thought I would pass this along because it is a weird problem, and could be very confusing to diagnose (I know).
Chris
