Yukon starting problems

[Biznass]

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.

 

[PaulC]

This is a general answer, not necessarily accurate for a Yukon: Most vehicle fuel systems have a particulate screen that filters out gross particulates before the fuel is introduced into the fuel pump. It's possible that the lowest section of the screen may be clogged with junk and not allowing fuel to flow into the pump when the fuel level is very low in the tank. When you increase the level of fuel in the tank, the fuel level overrides the clogged area and the pump can then feed fuel to the engine.

 

[PaulC]

Another thing: Most fuel pumps that are submerged into the gas tank rely upon surrounding gasoline to keep the pump cool. When you run the engine with a very low level of fuel in the tank, the fuel pump is running at a hotter temperature than optimal, which shortens its life span.