93 jimmy runs, then does'nt then does

This jimmy of mine is driving me crazy, I'v replaced plugs, rotor, cap, spider assy, nut kit, fuel pump, fuel filter and sometimes it will start right up and run fine other times it wont start and if you wait 10 to 15 minutes and try again it will start and run. Other times it will start up and immediatly quit running.I have 56 psi of fuel pressure and spark but it wont start, then as I said if I wait 10 minutes or so it will start up and run ok. Any help would be greatly appreciated. I'm running out of things to check.:banghead:

Does it stumble or run rough after starting ,seem rich?

Nope, runs smooth. Also I'v replaced the ignition mod. in the distributor. last night when I tried to start it I would turn the key and it tried to start as soon as I let off the key it would die, after trying this for about a half hour(taking breaks in between) I had drink turned the key and it started and ran fine like nothing was ever wrong:banghead: :screwy:

An update on this problem..I pulled the jimmy into the garage and had it in there for a week. Every time I tried to start it, it fired right up and ran fine. so I let it sit out side last night and got home from work and it started right up and ran fine. I turned it off went into the house, came out a half an hour later and the flippin thing would not start. It tries to start, but as soon as it starts it dies right away, I tried to start it 2 hours later and it started right up like nothing was ever wrong. This is making me crazier than I allready am..HELP ME,HELP ME

I think I'v finally got it. I bit the bullet and replaced the fuel pump again even though it showed 56 psi. Now its running fine. But I'm not sure if it was the pump or eliminating the pulsator or a bad ground for the tank/pump. None the less its running fine now..:smokin: