You've got the right equipment to do a proper test with that vac/press gauge. The most important result you're looking for is the amount of time the pressure and vacuum remain after stopping the engine. Those check valves used to be the most common failure items- - - -now the rubber parts in older pumps are failing due to "deathanol" additives to gasoline that create delamination and leaks, either into the crankcase or to the outside. A damaged diaphragm can fill the crankcase with explosive vapors, and/or dilute the oil enough to get rod and main bearing damage.

Good luck!

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!