PUMP NOT TURNING

This is an unusual occurrence, but it does happen.  

If you have a belt driven pump it will be quite obvious if the pulleys are not turning.  If this is the case check for a broken shaft of missing key on each pulley.  It's not so clear if you have a direct driven pump.  The key is what holds the motor shaft and pump shaft together.  If this slips out of place, or shears off, your motor will run but the pump will not turn.  

If the shafts are not damaged, replace the key and you should be good to go.  It is always a good idea to inspect the pump and motor keyway for damage.  Keys should fit snuggly in the keyway.  If there is wiggle room then you have a more serious problem.  

Shaft keyways can be fixed but this is risky, based on the cost to do it, if unsuccessful.  A fixed keyway on an engine shaft could take out the shaft of a pump if it fails.  Now, you have an engine, and a pump with a broken shaft.   

Crankshafts on engines and pumps can be replaced but it can be very expensive. You may need a new engine and or new pump if shaft damage is severe.