1997 GMC Jimmy Faulty Fuel Pump?

I have a '97 GMC Jimmy that I've been having problems with since last year. I replaced the fuel pump with a pump from the salvage yard last summer, replaced the filter, new coil, new ignition rotor, new battery, new distributor head. Just the other day, I cleaned out the carbon deposits from the EGR valve & bolted it back onto the engine. The truck will run and suddenly die. Sometimes it will start right back up, other times it won't. I can hear the fuel pump when I turn it on -- I'll start it up and it will idle just fine. But if I turn it off, and then turn the battery on again. I won't hear the fuel pump, the engine will start and instantly die (it probably uses the rest of the fuel in the line & runs out)
I've tried to replace so many things, when it does run occasionally it will seem like it's not getting gas and will sputter and the RPMS will jolt, and it will die. Other times, it will simply die. When it turns over and won't start, I know it's getting spark so it has to be fuel?

HELP!