Chevrolet Repair: 2005 chevy silverado 1500, chevy silverado, charcoal canister

Question
i have a 2005 chevy silverado 1500, with a v8 5.3, that will not start for about two hours after filling up with gas, what do you think may be causing this?

Answer
This is a good one.  Usually the problem is when the tank gets empty.  Then you say 2 hours later it is OK.  Does the truck do anything else?  

The standards are:  How is the fuel filter?  Try leaving the gas cap off and see if it will start.  Could there be debris in the tank that gets stirred up?  

My guess is VAPOR LOCK!!!!!  Here is my thought.  You have a vent on the tank.  This vent has a valve controlled by the computer.  GM is notorious for these valves failing.  If your is mostly shut or plugged up, your vent to the charcoal canister is probably overwhelmed by gas fumes from the fill up.  Putting on the gas cap removes the only vent your tank has once this other vent is not functioning.  Thus VAPOR LOCK.  Leave the cap off, I bet this helps.  The valve is found near the canister in the engine compartment, if this does prove to be bad.

C J S