You don't say whether you have a Monitor or Toyotomi lifter pump. Looking at the parts breakdown for the Toyotomi (
http://www.toyotomiusa.com/products/...s/OPT-91UL.pdf), there is the motor on top, a short plastic drive shaft (the "stick"), and a round pump assembly at the bottom of the tank. My guess is that the pump assembly has an inner rotor and an outer casing. Therefore, the pump shaft should rotate while the outer casing is fixed in place. Try turning the rotor gently with a screwdriver in the slot. Maybe something is jammed down inside, or it's just worn out. A pump like this has some sort of impeller that spins inside a round housing. The impeller will have flexible arms or vanes that slide in and out of a rotating hub. The arms/vanes must make contact with the inside of the housing. If you can figure out what's broken, you should be able to get parts from your local dealer or call Nelson & Small. This is all conjecture on my part, short of dismantling my own pump.