High Pressure Fuel Pump
| ITEM | DESCRIPTION |
|---|---|
| 1 | Fuel inlet - Low Pressure (LP) |
| 2 | Electrical connector |
| 3 | Fuel pump lobes |
| 4 | Exhaust camshaft |
| 5 | Pump plunger |
| 6 | Fuel metering valve connector |
| 7 | Fuel outlet - HP to fuel rail |
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 a fuel metering valve which is controlled by the ECM.
The HP pump is mechanically driven by the camshaft via a plunger. During the downward stroke of the pump piston, fuel is delivered to the cylinder at a pressure supplied by the fuel tank mounted 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 the HP outlet and a pipe.
The cylinder and LP fuel supply are connected via the fuel metering valve. If the fuel pressure in the fuel rail is sufficient, the ECM opens the metering valve during the compression stroke of the piston, decaying the pressure and directing the fuel from the cylinder back into the low pressure supply. A non-return valve is located between the fuel rail and the HP pump to prevent pressure dropping in the fuel rail due to fuel metering valve operation. The delivered fuel quantity depends on the engine speed and the actuation of the fuel metering valve.