I have a 1953 low pressure 235 in a big bolt truck. It has a Rochester "B" Carb and a double action fuel pump. I have had the fuel pump rebuilt by a well known shop in California, who for now shall remain nameless. I received the rebuilt unit back. Everything bolted up with no problem.
Fired up the truck and within 10 seconds was running, and in another 10 seconds, fuel was leaking from the accelerator pump linkage area of the carb flooding the engine and dousing the manifolds with raw fuel. I even had fuel spraying out of the air bleed. Pulled carb off and inspected needle and seat for wear. Saw nothing to suggest that was a problem. Checked the float setting and drop and all was well. Checked the float to make sure the float wasn't leaking or saturated. All good there too. Reassembled everything and fired her up again. Still flooded like crazy. Removed carb, took to a friend of mine's shop and he rebuilt carb, and went so far as to hook an electric fuel pump to carb while on the bench to verify proper sealing operation of needle and seat. All was well on the bench. Put rebuilt carb back on truck and still flooded and leaked all over. Then got a hold of a vac/ fuel pump guage and tee'd that into the carb. Fired truck up and wham! Within seconds, that fuel pump pegged the guage hard at 10 psi. Problem found. Called the pump rebuilder, and at first they said, send pump back and they would look at it. Seems fair to me. Then I received a call back from the rebuilder saying, that there was basically nothing they could do, because there is no internal adjustment in the pump that can regulate fuel pressure. The suggestion was made to put a regulator in the line to solve the carb flooding issue. I say no. The real question here is why is that pump putting out at least twice the recommended pressure? The fuel system in my truck never had a regulator installed, even when I used an electric pump. I have put a video on YouTube so you can check out what I'm writing about. It's about a minute and a half long. Here's the link:
The pressure output of the pump is controlled by the tension of the spring that pushes against the rubber diaphragm as the lever arm rides down the back side of the camshaft lobe. It's pretty obvious your "rebuilder" used the wrong tension spring when he rebuilt the pump and doesn't want to correct his mistake. That pump should be producing somewhere around 3-5 PSI and the pressure should stay on the fuel line for several seconds after the engine is shut down if the one-way valve in the output section of the pump is in good shape. There is also a vacuum check valve on the input side of the pump which will hold 10-12 inches of vacuum for a while after shutdown. Other than dismantling the pump and installing the correct spring, or using a pressure regulator, you're sort of stuck with a bad rebuild.
Edit: I just noticed your statement that you've got a vacuum booster pump. It's been quite some time since I've had one of them apart, but I think it's possible the spring for the vacuum chamber end and the one for the fuel diaphragm might have been reversed. Just a thought- - - -the only way to be sure would be to dismantle the pump and check the spring tension on a scale. Make one more try to resolve things with the shop before you open it up yourself. That would void whatever imaginary "warranty" you might have. Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
A number of years back I bought and installed a dual unit from Airtex or a name close to that. I had the same problem as the pressure was slightly over 6 lbs. The pump also leaked gas and oil and eventually I gave up on it.
