[IYAS9YAS]

The top portion of the pump was a vacuum booster that was capable of keeping the wipers operating, if its diaphragm was not ruptured.

Wipers ran off manifold vacuum pressure. When it dropped, on acceleration or under load, the wipers slowed or stopped. They didn't run from the fuel pump.

[editor-surveyor]

The 51 chev had a booster pump for when manifold vacuum was too low.