You have two, one way, valves in the fuel pump. As the diaphragm moves up & down it draws fuel in through one & pushes it out through the other. Pull the lines on both sides of the pump & turn the engine over while holding your fingers over both openings. If the suck side is sucking and the push side is pushing you have a blockage in the lines. If not the pump needs rebuilt/replaced.

Save a life, adopt a senior shelter pet.
The three main causes of blindness: Cataracts, Politics, Religion.
Name your dog Naked so you can walk Naked in the park.