Packard Forum Index » Post-War (1946-54)

I rebuilt the double action fuel pump on my '52 convertible, but I feel I must have done something wrong. When I let off the gas, the engine is rough and wants to stall, this will calm down after a second or two. When this happens, the vacuum goes too high and takes a couple seconds to reduce down to the right level. If I by-pass the pump and connect the two vacuum lines together, everything works fine, the vacuum is exactly was it should be.

I think this may be because I messed up the valves in the vacuum chamber. I used the procedures in the '52 manual because there were no instructions with the pump. In the vacuum side, I put the valve by the casting in with the "spiders" down,I also installed a valve in the hole in the bottom of the vacuum chamber the same way (legs down). The manual does not mention a valve in the hole in the chamber, just to replace the one by the casting. There had been a valve in the chamber when I disassembled it (but I didn't note which way it faced) and the kit came with 6 valves, so i assumed one needed to be there, but it does seem to not allow the vacuum to dissappate quickly enough.

I also note yesterday a small amount of oil leaking from the pump. It looks like the diaphram area, not the attachment to the block. I will tighten a bit.

I Did I assemble this correctly?

When you disconnect the hoses from the pump and put a finger over the ports, while the engine is running if the pump is working and valves are correct, one port will have suction and one will have a slight pressure. The port with suction connects to the wiper motor and the one with pressure to the intake manifold. To have vacuum being able to be pulled thru the pump enough to affect the engine with everything hooked up and wiper off would suggest a vacuum leak in one of the hoses or wiper motor.

Thanks Howard,

I do get one side of the pump with suction and the other with a very small amount of pressure. With the pump attached as suggested, upon accelerating, after dropping, my vacuum guage shows about 26 lbs, going down slowly to about 22.5. When I bypass the pump, upon accelerating, it drops quickly then returns immediately to 22.5. In both instances I am using the wiper line to attach my vacuum guage, so it should not be a variable. It does not seem like anything is different between the two tests except the pump itself. I wonder if reversing the valve would cause a vacuum leak n the pump.