motor won't start after sitting

I have a 1996 cobalt with a 454 efi. Starts up fine and runs good. Stop for hour and it will start up fine, until you take off then it dies and will not restart. Sit 20 minutes and it will start up and run fine until you stop again for any amount of time. Then you have to go through the same thing again, wait 20 minutes and it will run fine. As long as you keep going there is no problem. Dealer thinks I'm nuts. Any suggestion?

Sounds like, it's getting fuel,,, then it's not,,, then it is,,, then it's not,,, then it is,,, then it's not! Go over your whole fuel delivery system from the pickup tube in the tank with the screen at the bottom, then the one way anti-siphon valve (blow thru it both ways, to test). Then all your fuel lines, & filters. Next make sure your gas tank vent is not clogged by insects, or other debri (you can just take the cap off when having problems), and see what happens.

Once this is all checked out, it may eliminate your issues, and You'll be glad you did it fixed, or not, anyway.