in my experience the pumps are pretty much go/no go - start with the sound when you actuate the lever, will be a definite suck and blow - hold a finger over the inlet and work the lever, you'll feel the suction - then do the outlet, feel the pressure .... if it's the style where the body halves are held together with screws it's easy to open it up and look at the diapragm to insure it's clean and pliable - used to be kits available to replace those
the other thing to watch is if the end of the lever is worn a lot where it contacts the cam - what acts as failure sometimes is just that the arm isn't being moved a full stroke so apparent pressure is low
Bill
