My truck will run fine for a couple minutes then the power wire to the solenoid loses power. Then it will restart immediately for a couple minutes and shut off again. Truck is GMC topkick model year 1995. I was thinking maybe its a safety shutoff switch?
What makes you think there's a safety shut of switch? Are any of the warning lights on? I don't think the Cat people will be any help, cat just made the engine. There's no ECM, this engine should be all mechanical, just one wire to the solenoid, right? I'd look at any connections in the wiring harness, maybe leave the ignition on and a light hooked to the solenoid, but without the engine started, and see if you can duplicate the power shutting off by flexing the harness, connectors etc.
Look for a circuit breaker that's clicking off.....