The Stovebolt Site Forums The Shop Area Engine Shop GMC 302 fuel pump

I recently installed a new fuel pump in the 302 in my big bolt truck… I used a Carter M751. Is this an acceptable replacement? It appeared to be the same on the “engine side” of the pump as the one removed, but it will NOT pump. If I hook a squeeze bottle to the suction side of the pump, I can “force feed” it and get fuel to the carburetor and keep the engine running, but the pump will not feed. Lines have been flushed and pump is pulling with a hose from a gas can at bumper height..
I haven’t pulled the pump back out yet, but I’m hoping that the cam lobe being flattened is not why they parked this truck…
Any thoughts?

Will it pump if mounted in a bench vise and actuated by pressing the arm by hand?

If so, the cam lobe is probably gone and an electric fuel pump would be the easiest and cheapest fix.

If not, the new pump is bad, which wouldn't surprise me too much.

I haven’t pulled it back off to test on the bench, but when I pulled it out of the box I tried it and it seemed to “suck and blow” when actuated. I will have to remove it and get a visual on the cam lobe and bench test again.

If the cam lobe is the problem, do you suggest building a block off plate for the pump or abandon it in place? If abandoned in place, run the fuel through it still for ease of plumbing and original “look” or just route around it?

It did "suck and blow" the right direction, didn't it? It is possible to put the one-way valves in backwards in some fuel pumps and no telling how much training the pump assemblers had.

I'd pull the arm pivot pin, remove the arm, run a bolt through the pin's hole and put a nut and lock washer on the bolt to prevent oil leakage. Mount an electric pump near the gas tank and keep as much of the gas line as you can. The electric pump should push gas through the disabled mechanical pump with no problem.

I seriously doubt your cam lobe is wiped.

As has been noted many times on this forum, the mechanical fuel pumps available today are virtually ALL junk straight out of the overseas slave labor factories. Numerous fellow Stovebolters have experienced the same problem you're facing.

I experienced the identical problem you have and also thought my cam lobe was wiped. Two brand new pumps would not work. One failed to pump a drop of gas straight out of the box.

The solution is/was to locate an original mechanical pump or a reman pump from at least 30 years ago and either rebuild it yourself or have it rebuilt by a company like Then & Now Automotive.

My problem was solved as soon as I installed the rebuilt pump.

I don't know if the new pumps can even be fixed. In my case, it was obvious that on the first pump, the pump arm was assembled incorrectly. In other cases, the valves are installed wrong or not staked in position, the diaphragms are not made correctly and don't create enough suction or whatever. In some cases I think the pump arm may not have a long enough reach to activate the diaphragm fully.