High and Low Pressure Pump

High Pressure Pump:

The high pressure pump is a radial piston pump with three pistons arranged at an angle of 120° and an internal shut off valve located in one of the elements to assist with fuel temperature regulation. The high pressure pump is driven at about 1.3 times the speed of the camshaft. The high pressure pump is mounted to the front of the cylinder head and must be replaced as an assembly should a failure occur.

LOW PRESSURE PUMP

Vacuum Pump And Low Pressure Fuel Pump Assemblies:

The low pressure pump supplies an adequate quantity of filtered fuel in all operating conditions from the fuel tank, at an adequate pressure, to the high pressure pump.

The low pressure pump draws fuel from tank through fuel filter and supplies the high pressure pump. Fuel pressure at starter speed is 0.4 to 1.5 bar (6 to 22 psi.). A fuel pressure of 2.0 to 2.5 bar (29 to 36 psi.) is reached at idle speed. Fuel pressure is limited to 3.5 bar ± 0.5 bar (51 psi. ± 7 psi) by the valve in the fuel delivery pump. This valve opens by over coming a spring force and allows excessive fuel to flow to the intake side of the low pressure pump. This diverted fuel flows into the return flow pipe through the fuel cooler back to the tank. As a result of this circulation, the fuel always remains relatively cool.