I've got an 04 Yukon with 40k that does not want to start when low on fuel (less than 1/4) and sits for more than 8 hours. Just cranks and cranks. It will run fine at a low level and start right up with in a few hours of being shut off. When it doesn't start if I put a few gallons in it will fire. I can't see how this is the fuel pump since it runs fine at lower levels of gasoline and starts fine as long as it doesn't sit overnight. Anybody ever have this happen to them? Also I can hear the tank expand after being shut off after a long run. I'm wondering if this is a venting problem.