The definition of as Gas Locked Pump is both traveling and standing valves remain closed during the entire stroke. Gas Lock of a sucker rod pump occurs if the tubing pressure on top of the plunger is always greater than the pressure inside the pump chamber and if the pump chamber pressure is always greater than he wellbore pressure on the outside at the pump intake. The traveling and standing valve open if pressure below the valve is greater than the pressure above the valve.
High compression pumps, specialty pumps, tagging, and slippage through pump clearances cause the chamber into the tubing. Operators stating "my pump is gas locked" usually have pumped too much gas into the tubing, resulting in unloading all tubing fluids. Pump action has ceased and the classic dynamometer card "Gas Lock" shape of a gas locked pump is not observed.