High Pressure Fuel Pump

The High Pressure (HP) fuel pump is located on the top of the engine. The HP fuel pump is attached to the camshaft carrier with 2 bolts and sealed with an O-ring seal.

The HP fuel pump is a single cylinder pump which meters the fuel pressure according to demand requirements for correct fuel injection. The delivery rate of the fuel pump is adjustable by means of the fuel metering valve. The fuel metering valve is controlled by the Powertrain Control Module (PCM) with a Pulse Width Modulation (PWM) signal.

The HP fuel pump is mechanically driven by the exhaust camshaft via a tappet. The tappet is operated by a four-lobe cam on the exhaust camshaft. A spring installed on the outside of the plunger to hold tight the plunger and the tappet, and remain in contact with the camshaft. During the downward stroke of the pump piston, fuel is delivered to the cylinder at a pressure supplied by the fuel tank mounted Low Pressure (LP) fuel pump. On the upward stroke of the piston the fuel in the cylinder is compressed. If the pressure from the pump exceeds the pressure in the fuel rail the fuel is delivered into the fuel rail via a single HP fuel line.

The cylinder and low pressure fuel supply are connected via the fuel metering valve. If the fuel pressure in the fuel rail is sufficient, the PCM opens the metering valve during the compression stroke of the piston. The fuel is then directed from the cylinder back into the low pressure supply.

The HP fuel pump comprises a check valve, which is located between the pump plunger and the HP fuel pump outlet connection. The check valve maintains the desired fuel pressure in the HP side of the fuel system. The delivered fuel quantity depends on the engine demand, controlled by the actuation of the fuel metering valve.