Hand-pumping can often make a tired pump look good, because you're moving the diaphragm further than the camshsft lobe does. Loose screws will definitely cause problems- - - -air leaks. Try the volume check again after the teardown/reassembly, and I'll wager you'll get a lot more volume. Then it's time for a test drive.
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!