Pos. | spare part no | Name |
A | - | Low pressure fuel return to filter |
B | - | High pressure fuel supply - from the high pressure fuel pump to the fuel manifold |
C | - | High pressure pipeline - from the fuel manifold to the injectors (4 things.) |
1 | - | fuel manifold |
2 | - | PCV |
3 | - | Fuel rail pressure sensor |
The fuel manifold is made of forged steel and is attached directly to the cylinder head with two fasteners. The fuel manifold stores pressurized fuel from the high pressure pump. In addition, it prevents pressure fluctuations in the high pressure system. Holes at each end of the fuel rail are fitted with a fuel rail pressure sensor and a PWM type PCV. The pressure sensor is installed in the fuel rail on the accessory drive side. The PCV is installed in the transmission side of the manifold.
The high pressure fuel lines connect the fuel manifold to the high pressure pump and fuel injectors. bypass (returnable) a pipeline connects the fuel manifold to the fuel filter return circuit.
The fuel manifold, fuel pressure sensor and PCV form a single unit and should not be separated. If a malfunction occurs that requires component replacement, the entire fuel rail assembly must be replaced.
Fuel rail pressure sensor
At the end of the fuel rail (accessory drive side) installed fuel pressure sensor. It is connected to the ECM by the engine wiring harness. The pressure sensor has 5V power, ground and signal circuits. The pressure sensor in the fuel manifold is a piezoresistive one containing an actuating diaphragm. Diaphragm deflection provides the ECM with a proportional voltage output, depending on the fuel pressure in the fuel rail.
Pressure sensor parameters
Pressure sensor output voltage | Fuel rail pressure |
0,5V | 230 bar |
4,5V | 1 600 bar |
The ECM compares the sensor signal voltage with values in memory to calculate the actual fuel pressure present in the manifold. The ECM then uses the fuel rail pressure information to control the operating position of the VCV and PCV. For more information see the chapter: Electronic Engine Controls - 2.2L Diesel (303-14 Electronic Engine Controls - 2.2L Diesel, Description and function).
Pressure control valve (PCV)
PCV installed at the end of the fuel rail (from the gearbox side). It is connected to the ECM by the engine wiring harness. The PCV is a solenoid valve controlled by a 12V PWM signal. The ECM actuates the PCV to regulate fuel pressure in the fuel rail. The discharged fuel is directed through the fuel manifold bypass line to the fuel filter return circuit. Returnable (bypassed) the fuel provides cooling and lubrication for the PCV. For more information see the chapter: Electronic Engine Controls - 2.2L Diesel (303-14 Electronic Engine Controls - 2.2L Diesel, Description and function).
The PCV is normally open when the solenoid valve is not receiving power from the ECM. The resistance value of the PCV solenoid coil is 3.6 ohms at 20°C.
The PCV is also used by the ECM to provide direct control of the fuel system in the following situations:
- In the phases of a sharp transition in the engine speed level (e.g. when the accelerator pedal is suddenly released), when VCV operation is not sufficient to affect fuel delivery to the fuel rail.
- To control fuel pressure when the VCV is faulty.
- In the fuel heating phase, when the temperature of the supplied fuel is less than 40°C. The VCV is fully opened by the ECM and the high pressure pump compresses the maximum amount of fuel to raise the fuel temperature. The ECM then modulates the PCV to return fuel from the fuel rail to the fuel filter return circuit. The fuel is then recirculated through the fuel filter and returned to the high pressure pump.
- When the fuel supply temperature exceeds 70°C. The ECM modulates the operation of the PCV to depressurize the fuel rail, subsequently lowering the fuel temperature to protect fuel system components. Fuel returning from the fuel rail is directed to the fuel filter return circuit and back to the fuel tank.
- When turning off the engine, to gradually release the pressure in the fuel rail.
Comments on this article