Sorry about that. Somehow I missed the 13V at the pump part, so it's obviously not a relay or fuse. So if you're not getting fuel to the Schrader valve, either you have a plugged line somewhere along the way, or a bad pump. not much else it can be. I'd pull the pump and check all the hoses. Maybe one has popped off or has a tear in it causing the fuel to simply dump back in the tank. (I'm assuming the pump is running?, yes?) If the pump is not running, check to make sure you have a good ground. If that checks out, and the pump is not running, you have a bad pump.
Hope this helps.