LR3/Disco 3
FUEL RAIL PRESSURE CONTROL VALVE
The fuel rail pressure control valve is incorporated into the high pressure fuel pump. The control valve regulates the fuel
pressure within the fuel rail and is controlled by the ECM. The control valve is a PWM controlled solenoid valve.
When the solenoid is de-energised, an internal spring holds an internal valve closed. At fuel pressure of 100 bar (1450
lbf/in²) or higher, the force of the spring is overcome, opening the valve and allowing fuel pressure to decay into the fuel
return pipe. When the pressure in the fuel rail decays to approximately 100 bar (1450 lbf/in²) or less, the spring force
overcomes the fuel pressure and closes the valve. When the ECM energises the solenoid, the valve is closed allowing the
fuel pressure to build. The pressure in the fuel rail in this condition can reach approximately 1300 bar (18854 lbf/in²).
The ECM controls the fuel rail pressure by operating the control valve solenoid using a PWM signal. By varying the duty
cycle of the PWM signal, the ECM can accurately control the fuel rail pressure and hence the pressure delivered to the
injectors according to engine load. This is achieved by the control valve allowing a greater or lesser volume of fuel to pass
from the high pressure side of the pump to the un-pressurised fuel return line, regulating the pressure on the high
pressure side.
The fuel rail pressure control valve receives a PWM signal from the ECM of between 0 and 12V. The ECM controls the
operation of the control valve using the following information to determine the required fuel pressure:
Fuel rail pressure
Engine load
Accelerator pedal position
Engine temperature
Engine speed.
In the event of a total failure of the fuel rail pressure control valve, the engine will not start.
In the event of a partial failure of the fuel rail pressure control valve, the ECM will activate the solenoid with the minimum
Item Part Number
Description
1
-
Fuel volume control valve
2
-
High pressure fuel pump
3
-
Fuel rail pressure control valve
