I take it this is not the vortec V6 engine. Is this a true carb. or throttle body injector You need to do a fuel pressure test to see what the pressure is at the test port. If it is not high enough check for blockage in the fuel line. If it tests good check for injector pulse to se if you are getting power to open the injector. If you get pulse replace the injector if not repair the harness or pcm.
First you dont have a carburator, This Truck is a throtle body, You said gas is not getting to the plug then the motor will not start at all, But you said it will start but not stay running, With that be said I would check the securty side if this truck has security and the systen is on the motor will start and then stall, need to look further on this!! Thanks Bills On Broadway Team.