Land Rover Discovery Owners & Service Manuals

Land Rover Discovery: Fuel Rail Pressure Control Valve (PCV)

Fuel Rail Pressure Control Valve (PCV)

The fuel rail Pressure Control Valve (PCV) is located in a threaded port in the rearward end of the fuel rail. The PCV regulates the fuel pressure within the fuel rail and is controlled by the ECM using Pulse Width Modulation (PWM) outputs to the solenoid valve.

When the solenoid is de-energized, an internal spring holds an internal valve closed. At a pre-determined fuel pressure, the force of the internal 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 a predetermined pressure, the spring force overcomes the fuel pressure and closes the valve. When the ECM energizes the solenoid, the valve is closed allowing the fuel pressure to build.

The ECM constantly monitors the fuel pressure and activates the fuel rail PCV accordingly to control the fuel rail pressure within the required parameters. Relieved fuel from the fuel rail is directed through the fuel rail return pipe to the low pressure fuel filter return circuit.

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-pressurized fuel return line, regulating the pressure on the HP side.

The fuel rail PCV 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
  • APP sensor position
  • Engine coolant temperature
  • Engine speed.

In the event of a total failure of the fuel rail PCV, the engine will not start. In the event of a partial failure of the fuel rail PCV, the ECM will activate the solenoid with the minimum PWM duty cycle which results in the injection quantity being limited.



The Fuel Rail Pressure (FRP) sensor is located in a threaded port in the forward end of the fuel rail.

The FRP sensor measures the fuel pressure in the fuel rail which is supplied from the HP fuel pump.

The FRP sensor is a piezo resistor type sensor. The sensor receives a 5V reference voltage supplied through a resistor within the ECM and produces an analogue signal of between 0 and 5V depending on the pressure sensed.

LP gives a low voltage output and consequently HP gives a higher voltage output. The ECM uses this pressure signal to monitor the fuel pressure in the fuel rail and adjust the HP fuel pump fuel metering valve to control the fuel pressure in the fuel rail.

The ECM monitors the FRP sensor for faults and can store fault related DTC's. These can be retrieved using an approved diagnostic system.


     Fuel Temperature Sensor and Fuel Metering Valve

    Fuel metering valve Fuel temperature sensor Fuel Temperature Sensor The fuel temperature sensor is located in a threaded port in the HP fuel pump. The sensor is a NTC sensor which is connected

     Piston Cooling Oil Jets Solenoid

    The piston cooling oil jets solenoid is located on the left side of the cylinder block, below the thermostat housing. The solenoid is located in a port in the cylinder block and sealed with an O-ri

     Fuel Filter Assembly - Water in Fuel (WIF) Sensor

    Fuel filter ground connection Fuel filter inlet Fuel filter outlet Water In Fuel (WIF) sensor Fuel filter housing The water in fuel sensor is located in the base of the fuel filter and is har


     Fuel Charging and Controls - Turbocharger - Ingenium i4 2.0l Diesel Turbocharger Oil Supply Tube (G1875966) / Removal and Installation

    REMOVAL NOTES: Some components shown removed for clarity. Some variation in the illustrations may occur, but the essential information is always correct. Refer to: Cooling System Draining, Filling and Bleeding (303-03B Engine Cooling - INGENIUM I4 2.0L Diesel, General Procedures). WARNING: Make

     Wheels and Tires / Diagnosis and Testing

    PRINCIPLES OF OPERATION NOTE: Check DDW for open campaigns. Refer to the corresponding bulletins and SSMs which may be valid for the specific customer complaint and carry out the recommendations as required. For a detailed description of the Wheels and Tires refer to the relevant description and ope

    © 2019-2024 Copyright