Cause / 504

1. Coupling alignment. 2. Pump cavitates (sucking air). 3. Foot valve plugged. 4. Relief valve making excessive noise. 5. Pump shaft bushings tight.

Repair / 504

1. Re-adjust. 2. Check suction side of pump air leaks. 3. Clean screen and/or foot valve. 4. Clean and/or replace. 5. Replace pump.