When the engine is OFF, bias spring (9) holds pump swashplate (7) at maximum angle and movesactuator piston (8) to the left. No electrical signal is sent to pump control solenoid valve (5).When the engine is started, the pump drive shaft begins to rotate. This action causes barrel (11) torotate. Oil is drawn into the piston bores by pistons (12) as the pistons are drawn inward by thedecreasing angle of the swashplate.Pump control solenoid valve (5) consists of a solenoid that operates a small valve that redirects pumpdischarge pressure to, or drains actuator piston (8), which controls the angle of swashplate (7).Swashplate angle (displacement) determines pump flow rate under all pressure conditions.