i may just be a retard, but when i start the truck, unplug fuel pump wiring harness, unscrew gas cap, and then run the truck clean out of gas, how is it that the fitting on the fuel filter still pours out fuel like a hose? like i said i may just be a retard.

 

You lose pressure from the pump being unhooked. Engine stops like you're out of fuel but it's still in the injection system, although not under pressure enough to run the engine.

 

Remember it's not a carbeurator, but a pressurized injection system. As TNRabbit points out, it only runs until the pressure is lowered, then it leans out and stops. Even though there is plenty of fuel in the line.

Did you remember to leave the tank cap OFF when you removed the filter? The slowly evaporating fuel will apply enough pressure in the tank to push out, well, all of the fuel on a warm day. The vent in the fuel cap only runs in the other direction.

 

Siphoning from the tank through the pump.