Ditto on a bad fuel diaphragm. The lower unit with the bigger diaphragm creates the vacuum boost. Work the pump lever by hand with the pump housing clamped into a vise. The port that creates a suction needs to be plumbed to the wipers. The other port is plumbed to intake manifold vacuum. Those four holes are there to prevent a leaky diaphragm from flooding the crankcase with gasoline in case of a failure of the gas pumping part of the pump, which is what has happened. They're doing exactly what they were put there to do.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!