High Pressure (Hp) Fuel Pump
| ITEM | DESCRIPTION |
|---|---|
| 1 | Fuel pump shield |
| 2 | Bolt - Noise, Vibration and Harshness (NVH) cover (2 off) |
| 3 | Bolt (2 off) |
| 4 | Acoustic cover |
| 5 | High Pressure (HP) fuel pump |
| 6 | Exhaust camshaft lobe |
| 7 | Gasket |
| 8 | Cover assembly |
| 9 | Stud (4 off) |
The HP (high pressure) fuel pump is located at the rear of the engine and is driven off the exhaust camshaft. The pump is mounted on a cover assembly and secured with two bolts. The cover assembly is attached to the cylinder head, sealed with a gasket and secured with four studs.
The extended end of the exhaust camshaft protrudes through a hole in the end of the cylinder head. A three lobe cam on the end of the camshaft locates inside the fuel pump cover and drives a plunger attached to the piston of the fuel pump.
Because the high pressure fuel pump is driven off the engine exhaust camshaft by a three lobe cam, the piston of the pump cycles at 1.5 times the engine RPM. (Engine camshaft turns at one-half engine RPM multiplied by three for the number of lobes on the exhaust camshaft).
A shield is fitted to the fuel pump to protect it from damage and an acoustic cover is fitted over the pump to dampen pump operating noise.
High Pressure (HP) Fuel Pump
| ITEM | DESCRIPTION |
|---|---|
| 1 | Fuel metering valve connector |
| 2 | Fuel outlet - High pressure to fuel rail |
| 3 | Fuel inlet - Low pressure |
| 4 | Pump plunger |
| 5 | Tappet |
| 6 | Exhaust camshaft |
| 7 | Fuel pump lobes |
The HP (high pressure) 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 high-pressure pump is mechanically driven by the camshaft via a plunger. A tappet on the end each plunger is operated by a three-lobe cam on the camshaft. A spring installed on the outside of the plunger ensures the plunger and tappet remain in contact with the cam. 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 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 high pressure 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 LP supply. A non-return valve is located between the fuel rail and the high pressure 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.