I have taken the cap off for a similar amount of time to fueling and put it back and and it starts right up, it happens if I top it of, fill it until the pump stops automatically, or if I don't fill it all the way. It appears to be directly related to putting fuel in. I will run a gallon of denatured alcohol through it to see if there is water in the tank, but could it be something else?

 

Keep in mind that water is heavier than gasoline so it sinks to the bottom of the tank. If you have water in your tank and run your engine, that water won't stay in your gas tank for very long because it will be the first fluid to get sucked up by the fuel pump.

If you suspect the gas station you are going to is pumping water into your tank, I would go to another gas station as a test. This is extremely rare these days, and if it wasn't rare, everyone filling up at that station would have trouble driving off after filling up. That would make the local news pretty quickly.

In other words, I give it about a .000001% chance that water in your gas tank is the problem.

 

Faulty purge valve, stuck open probably, as you fill the tank the fumes which are displaced by the incoming fuel are pushed through the open valve into the intake manifold, so it kind of floods the engine.