VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1933-1936 What is the fuel pump pressure at the carburetor for a 33 Master

My car is a 1933 Master Coupe. The car has had a vapor lock problem in hot weather, and now the fuel pump doesn't pump the fuel up to the carburetor at all. I have ordered a fuel pump rebuilding kit from The Filling Station. But my question is what is the pressure supposed to be at the carburetor on a 1933 Master? I am considering installing an electric fuel pump at the gas tank to be controlled by a separate switch only when needed. I don't want to be left stranded anymore and no one would ever even know I had installed it if I don't mention it to them.
I am not interested in entering this car in any shows so that isn't a consideration.

Dennis Jones

Shoud be in the 3 pound area. Also check the volume by removing the line and see if it can pump out a good stream into a container (by turning over the engine with the starter)

Chev Nut....The fuel pump will only fill the sediment bowl at the pump about 1/4 of an inch. So I am pretty sure the pump is bad. I will rebuild the pump and maybe install an electric pump also. I am assuming it isn't a complicated job to rebuild the original pump.

Rebuilding the pump is quit simple. Ones you get it done, I don't think you will need the electric pump. Also the glass sediment bowl does not fill all the way up.

I have tested several rebuilt pumps in the past and their working pressure was 2.5 PSI.

Great responses from all. I thank you. Will let you know how it turns out after rebuilding the fuel pump. Ordered the kit today.

Jonda
I agree with previous comments but will add that there is the possibility of a blockage between the tank and the pump giving you the failed pump indication.
Tony

Tonyw......I agree there may be a possibility of a blockage. But when I pulled the tank out of the car when I installed the new sending unit last year the tank seemed to be in excellent shape. I will need to syphon the gas out of the tank and remove the fuel line at the tank. Then try blowing compressed air through the line. I have hesitated on that because there is probably about 7 gallons in the tank and we have a water heater in the garage. But it needs to be done and I will get after it.

That is one of the reasons for checking volumn as well as pressure.

You can blow back to the tank and not need to drain or spill any gas.

My recent experience my 35 standard had an aftermarket pump that did not allow me to replace the diaphram because it was riveted on. Not sure what the professionals do with them. I just wanted give you a heads up on what I had to deal with. I replaced the whole pump. I did see 6v "pusher" electric pumps that work with your mechanical pump attached. If you go that route be sure it's one that pumps only 3-5 lbs max. I saw some that said 5-7lbs. too. Good luck!

I have replaced the riveted type of diaphragm before. Grind off the rivet on the shaft, remove the old diaphragm, center drill the shaft and tap for a small machine screw and washer. Then, install the new diaphragm.

You can check the line from the tank to pump by applying a vacuum source (Mighty Vac or the good old fashioned way) at the pump end of teh line, and letting the fuel siphon into a container. You should get good, solid flow.
I rebuilt the pump on my '33 a few months ago because the old diaphragm was stiff and cracked. It was an easy job.

The glass bowl on the inlet side does need to fill up, other wise no fuel will flow to the carb.

After you are done, it may help to pre fill the bowl, or pull vacuum on the outlet side of the pump so you don't have to crank the engine forever to get gas to the pump.

PS. Put the motor in #1 TDC so the pressure is off the pump lever, and don't reinstall it with the lever on the wrong side of the cam.

Doug

If you are going to put air pressure blowing back from fuel pump toward the tank be sure to remove the gas cap first as this will restrict the air flow.

I would also blow out the fuel line first. I disconnected the fuel line at the pump and the gas tank and blow it out with compressed air.

Another issue that will keep the fuel pump from pump gas is the glass bowl seal. If the glass bowl is not sealed then the fuel pump is going to mostly pump air and not suck gas into the bowl.

Another issue is that the pump may be bent above the glass bowl. I had a fuel pump where the metal section of the pump was warped where the glass bowl fits to the pump. I ended up removing the pump and gently heat the metal with a blow torch and working it back into shape. If you do this be very very careful that you don't overheat the part and melt the pump, it got rather flexible. I assumed the previous owner had overtightened the glass bowl, which eventually bent the pump. After getting its back to shape I did a total rebuild of the pump.

It is common for the pressure that seals the glass bowl to the fuel pump over many years to warp the die-cast metal. Using a cork glass bowl gasket may be a "fix". If the casting it too warped then heating to ~ 400 deg. F with weight on the casting to push down and glass bowl in place (to serve as a support) can take out the warp. Too much heat will destroy the casting.

We found and purchased a 36 Town Sedan out of AZ last year. It would run great for a little while but then would crap out and barely run at all. I put a clear "jumper" hose made out of 1' of refridgerator drain tubing at the pump. It showed about 50% bubbles, which prompted further investigation. It turned out the pickup tube had rusted through in the tank. I replaced the tank with one offered through the FS. Only issue was with the filler neck, and reworking the connection for it. It still needs a little help and I am looking to improove the support for the filler neck at the body.

The whole filler assembly is supported by the rubber grommet that fits on the filler tube at the body. The tank is held firmly in place by metal straps on the TOP and on the bottom. These straps provide the ground for the sending unit to complete the circuit to the gas gauge in the dash. The positioning of the tank on these straps provide the correct spacing of the two part filler tube through the trunk floor, the side brace for the suite case rack, and the body. Install the tank first in a loose fit with the rubber grommet on the lower filler tube (tank to trunk floor) and then the top part of the filler tube with rubber grommet (upper filler tube with grommet to body). Use oil on the rubber grommet so it slides into place. Adjust and then lock the two parts together, then tighten the straps around the tank. This will provide the correct spacing of the rubber grommet on the body of the car. This is how I got my 36 Standard, Town Sedan's tank in place. Good luck with your project.