If the compressor won't restart after it fills the air tank, the check valve is likely stuck open. The check valve prevents tank air from back flowing to the pump. The stuck-open check valve causes high pump head pressure, preventing the compressor from restarting. Follow these steps to test the check valve:
Shut off the compressor and pull the ring on the safety valve to bleed the air from the air tank until it's empty.
Turn on the compressor to fill the air tank.
Bleed air out of the tank to reach the cut-in pressure, so the pressure switch attempts to restart the motor to refill the air tank.
If the compressor won't start with air in the tank, replace the check valve.
