6V electric fuel pumps

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The discussion on Pertronix lead to difficult hot start issues. Greg is right on about modern fuels and the tendency to boil the fuel out of the carburetor after shutting down. If you listen you can hear it percolating after shutting down on a hot day. I think this is also the problem of backfiring at closed throttle on hot days, the fuel in the carb bowl is boiling out when there is minimal flow screwing up the fuel level. The fuel evaporates out of all my carbureted cars after a week of sitting, and requires lots of grinding on the starter before fuel gets to the carb.

Years ago I had a classic 6V AC electric pulse (thumper) pump to pump fuel before starting. It lasted many years. The pulse pumps are convenient because the electric can be used in parallel with the mechanical and the check valves in each pump avoid requiring a separate check valve when operating only on the mechanical (I prefer parallel to more typical series as if vapor lock is a concern the pressure drop through the electric when not operating increases the suction ahead of the mechanical and would tend to increase vapor lock problems between them). Another nice feature of the thumpers are that you can tell that the carb has been filled when you hear the thumping slow down.

My problem now is the only 6V pulse pump I can find is the Airtex. I have had two now that failed within a couple months of installing. It seems to be electrical, not diaphragm failure as they quit making any noise.

Any thoughts on these pumps, have others had good or bad experience with them? Any alternatives? I want to keep operating on the mechanical and only use electric for priming and back-up. A friend talking to a parts guy claimed that a 12V thumper will work on 6V, which would open up the possibility of going to a longer lived new production 12V pump available for Jaguars. I might try it.

Thanks,

Jim

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