Fuel is compressed by pump pistons of 3 diameter direction that located angle of 120º each other inside high pressure pump. Because delivery stroke of 3 times occurs every revolution, driving force of low torque occurs, and is 1/9 time of revolution force that is required to run existent injection pump so that stress may be kept uniformly to pump running parts.To run pump, required power increases in proportion to pressure that is established to Common rail and speed of revolution (delivery amount) of pump. Setting pressure is 1,350bars, and output of power of engine is depended on injection amount of injector on the basis of this.

Therefore, can influence in generating power of engine if trouble occurs to pressure limit valve or fuel leak.Operation of high pressure fuel pump does piston of pump to do transfer (Stroke) up and down according to shape of cam by operation of drive cam. This time, low pressure fuel pump transfers to chamber of pumping element that pump piston is moving fuel to BDC(BDC) through inlet valve of high pressure fuel pump if transfer pressure is big more than unfolding pressure (0.5~1.5 bar) of safety valve.If pump piston pass this BDC(BDC), inlet valve is closed.

Because it is impossible that fuel escapes in chamber of pumping element, fuel is compressed more than delivery pressure. Increasing pressure opens outlet valve as soon as reach Common rail pressure, and compressed fuel go into high pressure circuit. Fuel sending with pressure is continued until pump piston reaches to TDC(TDC). And then, if pressure falls, outlet valve is closed. Fuels that is remained to chamber of pumping element is stretched and pump piston moves to BDC(BDC) again. Inlet valves opens as soon as chamber pressure of pumping element falls to low pressure fuel pump pressure low and pumping process is begun again.