Why did the pump suddenly stop working and won't start again?

Why did the pump suddenly stop working and won't start again?

1. Check the suction line for leaks or blockages.
2. Remove and inspect the valve; make sure it moves freely and is free of debris.
3. Check the blades and grooves for scratches, burrs, and wear.
4. Check the rotor blades for excessive wear and replace if necessary.
5. Shorten the vertical and horizontal distance between the pump and the liquid; remove the automatic nozzle.