3rd Gen, need to drain gas tank

Good point. There was some space between the cab and the access port on the tank, but I can't remember how much. I'm trying to find pics...

 

I would get a proper diagnosis before going to the trouble of draining the tank. It could be anything.

If it has bad gas in it, a secondary effect can be fouled plugs. So once you clear up the fuel issue check and probably change the plugs.

It will take FOREVER to burn all that fuel at idle, best bet is to drive some miles if the truck can handle it.