I had a sanborn commercial air compressor given to me a while back. I was told it didn't work but didn't really know why. I got it all wired up (it's 220) and the pump wouldn't turn over. So I pulled the belt off and the electric motor seems to run fine without being hooked to the pump. I tried turning the pump by hand and it was pretty tough so I pulled the pump apart and everything was intact but pretty gummed up so I cleaned and relubed it all but it's still pretty hard to turn by hand. I hooked it back up and the motor still won't turn the pump even if I leave the head off so that the pistons are exposed. I guess my question is how hard should the pump be to turn by hand? Is it possible that the electric motor is just warn out?