does the fuel system have a check valve?

Because sometimes when I park my truck facing uphill even for just 30 minutes or so, it tries to start, quits right away, then cranks over for a couple seconds until it gets gas (or that's how it seems, anyway) then it starts normally. Never this problem parking on the flat. It just seems to me like gas is draining from the engine back into the tank or something. Does that happen??

 

No, the fuel doesn't run back to the tank. The fuel lines should retain pressure when the engine is stopped. And even if it did not retain pressure as soon as the fuel pump runs the pressure should be right back up to normal.

 

there is a fuel interlock

when you tip vehicle upside down the fuel is closed off

but it is off for good until reset. would not cause your issue

 

You would have to be on a very steep steep hill with very little fuel in the tank to cause any pump pickup issues. The pumps normally are below the fuel level and never lose their prime.

 

My guess is the fuel pump is just getting tired.