Packard Forum Index » Pre-War (1899-1942)

there is a line that runs from the intake manifold to the top of the fuel pump and then a line that runs from the top to the cabin. I assume to power the vacuum wipes but why does it run to top of the fuel pump?

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That part of the fuel pump is a vacuum booster pump to provide vacuum to the wipers during periods of heavy acceleration when manifold vacuum drops significantly. Without it, the wipers would slow dramatically or nearly stop under heavy acceleration. Pretty much a standard feature of better cars from the 30s into the 50s.

THE PUMP HAS 2 DIAPHARGMS AND THUS IS CALLED A "DOUBLE ACTION" PUMP. The bottom diaphragm pumps the fuel, the top diaphragm creates vacuum as does the intake manifold. On cheaper cars Ford/Chev etc they only have the bottom half and the wipers are powered by manifold vacuum. When accelerating or climbing am hill vacuum is low and the wipers go slow (start of a poem??). Upscale cars have the double action pump so that when the manifold vacuum drops the vacuum section prevails and your wipers work better.

Electric wipers solved all that.