1994 GMC Sierra engine won't start

I'd use a fuel pressure gage on it, go from there. Some of the national brand autostores used to loan out a fuel pressure gage. Check for possible mil codes. When you first turn the key on, can you hear the pump run a bit? You could check voltage and ground at the proper terminals, fuel pump connector. How long since a tune-up? If you use a jumper wire with inline fuse from battery voltage to terminal G of datalink connector, the pump should run, just for testing. The info I looked at 5.7L engine.