Vapour Lock???

[JHarris1385]

Not everytime. But it seems to only luckily start after sometimes messing with the gas cap.

[Cobrajet]

I didn't pay much attention to this thread earlier because I don't own a GM vehicle. But, last might I got to thinking that your symptoms sounded a lot like my '82 Mustang. For over a year it would occassionally fail to start, or it would start, run for a minute, then shut down. I suspected fuel problems, too. But, it got worse, until finally it flat refused to start. Further troubleshooting showed no spark. Turned out to be the Ignition Control Module, a notoriously common failure item. A $30 part from NAPA. Replaced it and haven't had a problem since. Check your spark. Your Ignition Control Module (or whatever Pontiac calls it) is probably built into, or attached to, the distributor. Good luck.