VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1933-1936 1934 truck fuel pump

Somewhere, sometime, someone replaced the correct fuel pump ( a simple pump with no sediment bowl) with a substitute. The substitute is a figure 8 style, with glass sediment bowl on one side and the pump next to it. It looks just like my 49 flathead ford fuel pump, (except that has a cup to fit the rod to activate it).
My question to you knowledgeable folks is, will it work? I'm thinking the lever may not be moving the diaphragm enough to be pumping fuel at the right pressure.
I'm interested in a running truck, not a perfect restoration. Seeing as these fuel pumps can be hard to come by, what do folks replace them with.....that work?
Thanks

The pump yo describe sounds as if is probably a 1935-1936 pump. If it is it will work just fine it just looks diffeent. That style pump is easier to find than the 1934 pump.
To see if it is pumping gas remove the line at the carburetor and point the line into a container and turn over the engine with the starter. It shold spurt an amount of gas.

The truck starts, runs for 8 minutes, then dies. I have never gotten gas to flow though the line while cranking, either before running or after it dies. However, it does run for 6 minutes so it must be pumping at idle speed. I have blown out the line to the tank, and hear air bubbles. I have blown out the line to the carb, and it is clear. I have rebuilt the carburetor, and rebuilt the fuel pump. During its 6 minute life it runs great, 45 mph. When it dies, I can get it to fire up by pouring gas into the carb, and then it dies when it runs out. I have an electric fuel pump coming to help sort this out. At least then I will know if it is fuel pump related or not.

Thanks for the information that the fuel pump on it should work. I did notice viewing through the check valve hole, after removing spring and wafer, that the diaphragm moves up and down, about 1/4-3/8 of an inch. That seems minimal to me, but then I am used to 10 PSI pumps not 2 PSI pumps.

I also have a plastic insulator coming to replace the wafer one between the carb and manifold.

My goal is to get it all running, then start isolating the problem(s).

I'm still smiling....and having great fun....but get delays as I get called to work 2 weeks Harvey, and perhaps Irma....we will see.

I bought this sweet heart to keep me busy.....and she has !!

I would think 1/4" to 3/8" diaphram travel at full stroke is more than sufficient for any pump (2 or 10 psi) as the spring determines the pressure. The cam pulls the diaphram against the spring which then pumps the fuel through. If only a little fuel flows before the cam next pulls the diaphram it only travels that distance but if a lot of fuel has flowed the diaphram travels further.
Tony

Hope you are making progress troubleshooting this problem.

I know this may sound crazy but this almost seems like the fuel tank vent is not working very well. It could be partially blocked or if it is fully blocked there is enough leakage around the fuel cap gasket that air will slowly get into the tank over time.

After the truck sits overnight there is plenty of air in the fuel tank to let fuel flow so the truck will start. After 6 or 8 minutes the engine has pulled enough fuel that air needs to replace it in the tank. The vacuum in the fuel tank prevents fuel from flowing to the fuel pump.

A quick way to test this is to loosen the fuel cap either before you start the truck or after it has stalled for lack of fuel. If the truck keeps running or you hear air rush into the tank then the vent is probably the issue.

By the way, lots of great posts going on in this forum these days.

I think even if the tank ventilation is totally blocked it would be a lot longer than 10 minutes running to use enough fuel to have that much effect. I am not saying not to investigate that possibility though. A floating object in the tank blocking the pickup temporarily and floating away when there is no pump action.
Tony

I will check it out when I get back. However, before I got the truck they replaced the filler neck, but not whatever seals it to the tank.....which I discovered the first time I filled it....gas all over the ground. Makes me think that even if it wasn't venting correctly.....plenty of air passage was still available....

Let me bring this thread to an end as well. Back from the hurricanes. I installed an electric fuel pump, and all seemed well. The the same vaporlocking symptoms occurred. Indeed, it was vapor locking. However, the reason was the tank had crud in it, and restricted the fuel pumps ability to pump. Allowing the gas to not flow well to the carburetor, and vapor locking. This was discovered when I installed a one gallon gas can under the hood for the electric pump to pull from. The truck ran great. Consistently. A new fuel tank, the jelly was just too hard to get out of the center area, and a new fuel line, and the truck ran super. Next I will pull the electric fuel pump, and use the mechanical one, because it probably was just fine after I rebuilt it. I’ll keep the electric pump as a spare.

Again, my thanks to everyone who posted ideas for me to check out. Humility is a gift.
guy