Hey all new member here and I really need some help here. I have a freshly rebuilt Pontiac 400 engine that I finally got ready to fire a couple days ago, but for some reason the fuel pump is not pumping fuel. First of all it's a brand new Holley 80 gph mechanical fuel pump driven by the eccentric bolted to the camshaft. At first I thought maybe the pump wasn't working properly, so I bolted up my original fuel pump which I know was working fine before I rebuilt the engine, and same thing, no fuel. Now I have tested both fuel pumps off the engine and they work fine. I was able to pump fuel from a gas tank by manually pressing the lever and both pumps work as they should. I am completely baffled because I have no idea why all of a sudden they wouldn't be pumping when attached to the engine. I removed the timing cover twice to verify the eccentric was installed in the correct position, and it is offset as it should be, but for some reason it seems the fuel pumps are not being pumped as the engine rotates, like the lever is not being pressed down far enough. I am using the same eccentric, same timing cover, and same fuel pump as before when it was working properly, and the new fuel pump is doing the exact same thing. Anyone have any idea what would cause a fuel pump to not be pumped while on the engine? I'm completely stumped.