No Start 6.5 Diesel Hummer H1

[Carbine]

Verify power at the fuel shutoff solenoid on top of the fuel injector pump.
If you have power then connect and disconnect that live circuit and see if you hear a click at the solenoid. That should tell you that you have a good solenoid. Not always but a 90%ter.
Don't be too quick to blame the glowplug controller, some of those can be bypassed. If you want to be sure if your glowplugs are cycling just watch the volt gauge and look for the drop and if it does you are cycling.

Chances are if the truck was running you lost power to the shut off solenoid somehow.