Thread: Pontiac 400 no fuel from fuel pump!

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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.

You are in luck. I had the same problem with a chevy 350. Turns out the bore for the push rod got galled ( ? somehow ? ) by the machine shop.

Not unusual for a mechanical pump to not pull fuel through a dry line.... Try priming the pump, or fill the float bowls with fuel so the engine will run long enough to pull the fuel up to the pump. Another way is to pull the fuel line off before the pump, blow air in the tank til fuel comes out the hose, and reconnect it...

oh wait.. pontiac doesn't use a push rod for the fuel pump does it?

sorry. Are you sure there is gas in the tank?

Check the fuel hose for dry rot.

Put a length of clean fuel line on, and see if you can blow through to the tank. ( take the gas cap off first ) Listen for bubbles.

If memory served me correctly, Pontiac fuel pumps have an arm on them that is pumped like a handle up and down by the eccentric. If the suggestions about prime and all are not the solution, then evidently for some reason the arm is not being pumped by the cam.

I would go back to the cam and make sure the eccentric is contacting the arm properly, and verify that it is actually moving the arm up and down. I have had situations in the past where I thought I had slipped the pump in straight, but actually had the arm on the wrong side of the eccentric. Won't pump that way.

Don