"I'll bet that the impeller is either worn, or is off the spindle at the end
of pump, or the
spindle is just spinning in the impeller."

I agree with Malcolm. Just because the pump is whirring does not mean it's
pumping water. When mine "broke", the end of the pump had come off (plastic
piece) so the impeller had fallen off the pump shaft.

Have you held the pump in your hand while the faucet is on to look at
exactly what's happening with the pump? If not, open up the tank, pull the
pump out, turn the faucet on while looking for the turning impeller and see
what's up. If it's there and turning, put it into a cup of water and see if
the hose fills with water .... or ...... ?

As odd as this sounds, when I repaired mine it was squirting water back out
the bottom of the pump. I could feel it while the pump was on, in the tank,
like a jet of water.... and no water coming out of the faucet.  Never did
figure out why that happened because, if I remember correctly, you can't
install the impeller backwards on that shaft. It would put it "upside down"
and the end of the pump won't fit back onto the pump body that way. Very ???
situation and I've never understood
why that happened.

bob