cranks nut wont sart

I have a 95 ram 1500 truck 5.2 that has a blown head gasket. Truck still runs but sometimes going up hill it just shuts off. Gottah wait a few hours before starting again. havent been driving it cause i dont wont to cause more damage to it. My truck has been sitting for awhile on a empty tank of gas.. but still starts up. Try to run in twice a week. But now that i decided to sell it... IT WONT START!!! The went to take it for a test run... We but $8.00 gas in it first.. Drove it a short distance.. right when we came up a small hill car died out and would not start up ever again. Cranks but cant sart... Please help