The Stovebolt Site Forums The Shop Area Engine Shop 216 fuel pump

I've been working on a 1951 Chevrolet 3100 with the original 216. A few days ago the truck died and would not restart. Figured out it was not getting any fuel from the pump. There was plenty of fuel getting to the pump, but nothing coming out the other side.

So I ordered a new pump and installed it yesterday, and still no fuel. Had fuel to the pump since it comes off the bottom of the tank it would come out the line with lots of volume.

Finally took the new pump off, and tried to work it manually and found it was trying to pump out through the inlet, and pull in through the outlet.

Replaced it with another pump today (warranted the other one) and before placing it on the engine, I decided to test it. I filled a clear bottle with some fuel, dropped a hose down in it and hooked it up to the inlet side of the pump. Within just a few pumps I had fuel coming out the inlet. Good I thought.

Put it on, no fuel.

I still had plenty of supply, so I unhooked the outlet, and cranked the engine while I watched to see if any fuel ever came out. Nothing. Put my finger over the outlet, and nothing. Not even air.

It acts like the cam lobe that drives the pump is bad. Are these engines known for the fuel pump lobe on the cam flattening?

I have an electric pump (low volume) on it and it runs like it should.

Thanks

Fuel pump lobes can wear out, but it's a rare occurrence. Use an inspection mirror and a bright light to look into the fuel pump hole while someone taps the starter pedal repeatedly to see if there's a high spot left on the cam. (No, don't stick a finger in there!)
Jerry

One other trick I plan to try tomorrow, I have a small fuel tank off a riding mower with the outlet on the bottom of the tank. I'm going to hook up a hose from it to the fuel pump and let gravity feed fuel to the pump, and crank the truck over and see if it moves fuel then. If it does then there must a leak some where in the fuel line between the tank and the pump.

If it doesn't pump fuel with this method, I'll do the mirror and light challenge and have my daughter crank the engine.

Thanks. I can't remember ever seeing a lobe for the fuel pump flatten out on these old sixes, but did see one do that on a 350 V-8. But for me at least it is pretty rare.

One thing that's confusing me- - - -you keep talking about fuel coming out of the "inlet"- - - - -is that a mistake in semantics? I hesitiate to suggest doing the vacuum and pressure test that's the normal way to evaluate fuel pump function, since nobody in my memory has ever tried it in the almost 20 years I've been talking about it on this forum!
Jerry

First fuel pump I installed, would not pump. I finally took it off to manually work the arm. Putting a rubber hose on the Inlet side of the pump and working the arm I would get bubbles. Like it was pumping air. So i placed the rubber hose on the outlet side and it picked up fuel and pumped it out the "Inlet side". First I have ever seen, but that's what it did.

I already had another pump coming so traded it out.

Doing the same test I could get fuel out of the pump using the "Inlet side" and it would pump out the "Outlet". That was what I wanted to see with the first one but didn't. But on the engine it will not move any fuel even though gravity is providing fuel to the pump.

So with the first pump I think the valves inside were installed wrong. With the second pump it works off the truck if you manually operate the lever. But does not work when installed on the engine even with the fuel dribbling out the inlet line when disconnected. It's getting fuel, not pumping it while on the engine.

This why I think there is a problem with the cam lobe.

Right now I have a low volume electric pump on it pulling through the same line and it works fine.

Seen a lot of stuff over the years, but never seen a flat fuel pump lobe on the camshaft on one of these old sixes, but I can't seem to find any other explanation.