Ok guys...here is one for you.

2000 F-350 Supercrew 4x4, 7.3L.

It fires up and after 20-30 secs or so, the truck dies, completely shuts off. You can crank it and it wont fire up. If you wait for 10-15 mins or so, it will fire up and run for a few secs, then die. Truck has 120,000+ miles. Anyone have any ideas? Its my to be father in laws and i was just trying to get some direction before he takes it in.

Thanks.

 

Sounds sort of like the CPS sensor has gone out. They're known for failing on the 7.3L to the point where alot of guys carry spares with them. Some last a long time, other last a few thousand miles. Also some will die slow intermitant deaths, others go out instantly and never work again. But the symptoms you're describing sound about right for a CPS failure.