Reply To: fuel pump pressure

#468057

Dave, thanks. Interesting, they manage to miss 1935 845 but presumably it is supposed to be the same as 1934 with the 2 psi pressure, although just to add to the confusion the original mechanical pump on mine will pump to over 3 psi, which should be determined by the spring force of the fuel pump diaphragm.

My EE-3 with the original stainless steel needle (no rubber tip) resisted over 4 1/2 psi without apparent leakage to my surprise, but discretion being the better part of valor I will keep things at a lower pressure. 4 1/2 psi cold won’t be the same as when a hot carb bowl is boiling.

Several years ago I witnessed the percolation phenomena when I was testing the new radiator core in summer heat – no fenders or hood. When the engine was nearing vapor lock I found the left side idle mixture adjust screw had no effect, and peering  trepidatiously down the carburetor I could see liquid fuel burping out of the main jet on that side from boiling. It would have been unpleasant if it had backfired at that moment. I am rethinking potential auxiliary electric pump system changes before the hood and fenders go on making changes inconvenient.