Fuel pump only works using primer...

[geekeasy]

I'm trying to get my engine running again after half a rebuild.

There seems to be an issue with the fuel pump. I can pump fuel through it with the hand primer, but when I'm turning over the engine just using the starter it doesn't pump any fuel at all.

Any idea what might be wrong?

Thanks!

[geekeasy]

P.S. This is the mechanical pump. And by primer, I mean the built-in lever on the side.

[Dave Neptune]

When you "rebuilt" did you remove and replace the plunger that pushes on the pump arm?

Dave Neptune

[ndutton]

My first thought too. Confirm the integrity of the push rod that rides against the camshaft.

[geekeasy]

You guys are both right.

I found the part, but it's a bit rusty. I've sanded it down but I'd rather replace it.

Does anyone know the actual name or better yet a part number for the pushrod or plunger?

[ndutton]

Available from Moyer Marine:

https://moyermarine.com/product/mechanical-fuel-pump-push-rod-used-fpmp_13_366/

[capnward]

If you rebuilt the fuel pump, I found this old jpg file showing how the pump can be reassembled incorrectly. Maybe this happened to you. Note the 'incorrect' orientation of the bar connecting the pushrod to the diaphragm. I'm not sure how this works, never having taken my pump off the engine and looked at this mechanism. It looks as if the diaphragm would not go up if the bar is installed that way, but the bail would still move the diaphragm. Hope this helps. The pushrod looks like a very simple part that not much could go wrong with, but maybe it wore down. I thought crankcase oil would have kept it from going rusty, and not sliding well as it emerges from the engine. Good Luck, and keep us posted.