1957 fuel pump vacuum

[Tom Piantanida]

My 1957 has a miss at idle, so I started checking for a vacuum leak. I found that if I plugged the line from the vacuum port on the intake manifold to the inboard vacuum port on the fuel pump, the engine ran better. My question is whether the dual-action fuel pump will create sufficient vacuum to operate the heater control with the input (?) vacuum line from the intake manifold plugged. OBTW, I have electric wipers.

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[Tom Alpers]

If I'm reading you right, I think you have the problem backwards... If it's running better with the line to the vac pump disconnected at the manifold and blocked there must be a leak somewhere downstream from the manifold connection. The proper approach is to find the leak and fix it. Possibly the vac pump on top of the fuel pump itself has a leak, or the heater vac control valves (one on the heater core and one on the manifold). Any chance you didn't plug the end of the vac line that used to go to the vac wiper motor? What I would suggest is you get a $15 vac pump from harbor fright. They sell one in a kit for bleeding brakes. It works great to pull a vacuum in these kinds of vac operated systems. Put the pump on the line that would otherwise connect to the manifold and move it progressively downstream till you find the leak, if there is one. Back to your original question if you just want to disconnect from the manifold and use only the vac pump... I think the most you can get that way is about 10 inches of vacuum. I would think that's enough to run the vac valves for the heater but that's just my guess.

 

[Pink T-Bird]

My 1957 has a miss at idle, so I started checking for a vacuum leak. I found that if I plugged the line from the vacuum port on the intake manifold to the inboard vacuum port on the fuel pump, the engine ran better. My question is whether the dual-action fuel pump will create sufficient vacuum to operate the heater control with the input (?) vacuum line from the intake manifold plugged. OBTW, I have electric wipers.

I agree with Tom. Although you can probably do the same troubleshooting without a vacuum pump using your engine as the judge of where the leak is. Start with the metal Line to the fuel pump connected to the motor and blocked before the fuel pump then add a section at a time until it runs poorly again.