Fuel Rail Pressure Control Valve
The fuel rail pressure control valve is located in a threaded port in the rearward end of the fuel rail. The pressure control valve regulates the fuel pressure within the fuel rail and is controlled by the PCM 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 pre-determined pressure, the spring force overcomes the fuel pressure and closes the valve. When the PCM energizes the solenoid, the valve is closed allowing the fuel pressure to build.
The PCM constantly monitors the fuel pressure and activates the fuel rail pressure control valve 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 PCM 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 PCM 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 high pressure side.
The fuel pressure control valve receives a PWM signal from the PCM of between 0 and 12V. The PCM 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 pressure control valve, the engine will not start. In the event of a partial failure of the fuel pressure control valve, the PCM will activate the solenoid with the minimum PWM duty cycle which results in the injection quantity being limited.