High Pressure Fuel Pump
The high pressure fuel pump is a mechanical one-cylinder design driven by an additional three lobe cam on the camshaft. High pressure fuel is regulated by the fuel rail pressure (FRP) regulator, which is a part of the high pressure fuel pump. The FRP regulator is a magnetic actuator which controls the inlet valve of the high pressure pump. The ECM provides battery voltage on the actuator high circuit and ground on the actuator low circuit. Both circuits are controlled through output drivers within the ECM. When deactivated, both drivers are disabled and the inlet valve is held open with spring pressure. When activated, the actuator low circuit driver connects the low circuit to ground and the actuator high circuit driver pulse-width modulates (PWM) the high circuit. The ECM uses the camshaft and crankshaft position sensor inputs to synchronize the FRP regulator with the position of each of the three camshaft lobes. The ECM regulates fuel pressure by adjusting the portion of each pump stroke that provides fuel to the rail. The high pressure fuel pump also contains an integrated pressure relief valve.