Take the punp off and rig a magnetic base dial indicastor so the plunger bears against the cam lobe. Turn the engine (by hand if possible) by removing the spark plugs and pulling on the fan blade. In two turns of the crankshaft the pump cam lobe will make one full cycle. I've got a few camshafts I can set up in my lathe and give you a specification for what a normal amount of lobe lift should be. It's far more likely thst you're getting "new" pumps that are defective, given where they're most likely coming from.
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!