2003 silverado 2500 hd

cranks but no start sometimes it starts right up and runs for a few min to a few hours then just stops may start right up or it may take about 30 min have done the passkey reset still have the same problem

You need four things to run. Fuel, ignition, compression, and timing. You need to do some diagnosis when it won't start to figure what you don't have.

Basics as Stealthee says, I would get a fuel pressure gage on it and look for at least 55 psi, cranking.