A lubricant pump comprises a shiftable control ring, a pump rotor rotating in the control ring, a pump outlet, and a pressure control system. The pressure control system comprises a pressure control chamber which pushes the control ring into a high pumping volume direction, an engine pressure input port connected to an engine pressure output port of an engine, a pilot chamber connected to the engine pressure input port which pushes the control ring into a low pumping volume direction, and a pressure control valve which controls a pressure in the pressure control chamber. The pressure control valve comprises a control valve plunger which opens/closes a control port to connect/disconnect the pressure control chamber to the atmospheric. The control valve plunger is fluidically connected to the engine pressure input port so that the control valve plunger is pushed by a lubricant pressure of the engine into an open position.