The engine will crank and run as long as you keep the key held to keep starter engaged,when you turn loose the key it will go dead.Is the problem the key switch or something else?
Thanks

 

kes the key switch is bad ...to test it.....run a wire from the + side of your battery to the + side of your coil and start the truck if it runs then the switch is bad...but remember you need to puill the wire to turn off the truck