Moving my compressor into my new shop.....moving with appliance cart and the tire goes flat all the sudden. Compressor started to slide off the side and I caught it but it was too heavy and had to drop it to the floor from about 12 inches on the floor. broke the cast pulley on the pump. Ordered a new pulley from MT and fired it up. It started as usual and about 20 seconds in it starts to bog down and then sounds like it is going to come out of it and then bogs down again. This repeats several times until it finally stops the motor to a hum and I shut it down. I have no idea what could be the problem. It has no air in the tank. This is a fresh start up with an empty tank. So what is it? Capacitor? Unloader valve? Check valve, valves in pump? The pump turns like it should when I turn it by hand. I took the belt off and fired it up and the motor runs and sounds as it should with no load on the pulley. HELP! This is driving me nuts.

Thanks for replying. It did sit on its side for a couple hours before I had someone to help me get it off the ground. The drive belt looks to be ok. How will I know if there is hydraulic lock? My sight glass shows my oil level is ok if that makes a difference.

Also, when I take the pipe off between the pump and tank it runs fine. I looked at the deflection in the belt and it looks right about 1/2". Thanks for the help. I had my HVAC guy test my capacitors, so I know that isn't the problem.