What would typically cause one of our cars to start fine, run fine, but then once you turn it off, it will not start again until you let it sit for a long time.

 

Could be a heat soak issue with something in the ignition system (ICM module) or a flooded engine. Try holding the gas pedal to the floor when starting. This will cause the computer to go into flood mode, supplying less fuel during startup.

 

Just to give some more details... It's my brothers 99 Formula. Stock, except for headers that were put in this past summer. The car will start fine and drive like nothing is wrong, but when he gets to where he's going and turns off the car, he won't be able to just start it back up and come home. I'm not sure if maybe he has to wait until it's cool enough or what, but it won't start right back up. He has also been putting crappy Sheetz gas in a few times even after it caused him to have some rough starts and rough idles... I don't know if that plays a factor or not.

 

What EXACTLY do you mean by "it will not start"? Does the starter engage? Does is crank the engine? Does the engine attempt to start at all? Does putting your right foot on the floor (clear flood mode) make any difference?

 

This post is actually about my bros LS, not my LT, so I guess this should have been moved to the LS section, not here. My bad, I should of put that info in the first post. But I'm not sure about the clear flood mode yet. All I know is what he told me so far... I'll find out and post up again.
Thanks