The Stovebolt Site Forums The Shop Area Engine Shop Starved for fuel

I have a strange problem with my 54 3100 235. I thought it was a bad fuel pump. Now the new one is doing the same thing. I can drive it for long periods with no issue. Then, without warning it starts cutting out as if it is starving for gas. I have an electric booster pump that is capable of operating on it's own or to supplement a mechanical pump. I installed it to help prime the fuel line when the truck has been sitting for a while. I have the electric fuel pump on a toggle switch. When the truck starts cutting out, I can flip on the electric fuel and the engine will smooth out and I can keep going. If I do not turn on the electric fuel pump the engine will die. I can wait a few minutes and it will start back up. When I turn the electric fuel pump on, I can turn it off again after a minute and the truck keeps running fine until the next time it decides to cut out. If I leave the electric fuel pump running, the engine will go forever without cutting out. I am going to use the dreaded phrase. Could this be "vapor lock" and the electric fuel pump is powering through the issue?

True vapor lock is about as rare as finding the Easter Bunny, a chicken with lips, or an honest politician. You've probably got a bad inlet check valve in your mechanical fuel pump. Quite often, it's caused by debris from the fuel tank getting lodged in the valve and preventing it from working properly. There's a test to diagnose that problem that I've been describing for 20+ years on the forum, but it's one that few, if any bolters appear to be willing to do.
Jerry

That points back to an issue in the second mechanical fuel pump that is doing exactly the same thing the previous fuel pump was doing. I don't doubt that could be the issue, just a strange coincidence that 2 fuels would both have the same defect. I now wonder if the obstruction/issue could be in the electronic fuel pump. It is suppose to allow gas to flow freely through it regardless as to if it is turned on or not but I wonder if when it is turned off it is restricting flow.

Putting a fuel filter on the inlet side of the mechanical pump might solve the problem, if indeed it's debris from the tank causing the pump to malfunction intermittently, but make it a BIG filter so there's minimum restriction. I like to use the big Ford fuel injection system filter that's about 3" in diameter, with a steel canister. Hide it under the cab near the fuel tank outlet- - - -out of sight, out of mind!
Jerry

I can try that. It would be an easy fix. Not a lot of effort wasted if it does not solve the problem. I do have a brand new fuel tank and fuel lines.

Put a temporary rubber fuel line in to by-pass the electric pump and see if that fixes it.

Mike B

Put a temporary rubber fuel line in to by-pass the electric pump and see if that fixes it.

Mike B [/quote]


X2

It's not a coincidence. Modern "new" fuel pumps are all garbage made in China. I have had the same problems with mechanical pumps for 50s Cadillacs, 70s Fords, and the AD truck. Two brand new pumps for the AD failed straight from the box.

You will need to have your original pump properly rebuilt.

Did you install a new sending unit in your new tank? If so, did it have a flat sock plastic strainer on it? Mine did and the sock would collapse and restrict the fuel flow to a starved for gas condition. After several episodes just like you experienced I removed that sock and replaced it with the stainless wire strainer from my old sending unit... end of problem.

The gas tank is under the seat in my 39. I installed a sediment bowl where the fuel line comes out under the cab. The sediment bowl has a shut off valve. The fuel line goes from there to an electric fuel pump then to the mechanical pump. The electric fuel pump has a toggle switch under the dash. I use the electric pump when the truck has been sitting for awhile. I started to get a lot of debris in the sediment bowl, so I installed a new gas tank. This set up has worked well over the years.

Rick