Fuel System Component Overview
Fuel System Component Overview
The control module for the diesel direct fuel injection system is equipped with a Diagnostic Trouble Code (DTC) memory. Before and after repairs or adjustments, the DTC memory must be checked. Refer to the vehicle diagnostic tester.
• Follow the guidelines when working on the fuel system. Refer to => [ Safety Precautions ] Safety Precautions.
• Follow the guidelines for clean working conditions. Refer to => [ Clean Working Conditions ] Clean Working Conditions.
• Always follow these rules before and during work.
Follow the points below to avoid running the high pressure fuel pump dry and to start the engine quickly after replacing the components:
• It is necessary to perform the "check the transfer fuel pump" basic setting "once" to bleed the fuel system before starting the engine for the first time if the fuel pump, a fuel line or the fuel filter was removed.
• The "check the transfer fuel pump" basic setting must be performed "three times" for bleeding the fuel system before starting the engine for the first time if the high pressure fuel pump was removed or replaced.
Maintain clean working conditions. Dirt and contaminants must not get into the return lines and the connections on the fuel injectors.
Always protect any opened fuel connections to prevent dirt from getting into them.
1 Protective Strip
• For the fuel rail and high pressure lines.
2 Fuel Return Lines
• With a pressure retention valve.
• Checking the pressure retention valve. Refer to => [ Fuel Return Line Pressure Retention Valve, Checking ] Testing and Inspection.
• Pay attention to the different installation stages. Refer to => [ Fuel Return Line Differences ].
3 Bolt/Nut
• 8 Nm
• Allocation, refer to => [ Connection: High Pressure Line between the High Pressure Pump and the Fuel Rail ].
4 Fuel Return Line
• Blue or with a blue mark.
• Make sure it is secure.
• To the fuel filter.
5 High Pressure Lines
• 28 Nm
• Between the fuel rail and the fuel injectors.
The high pressure lines can be reused only after the following checks:
• Check the sealing cone on each high pressure line for damage and deformation.
• The bore in the line must not be deformed or narrowed.
• Do not use corroded lines again.
• Install without tension, refer to => [ High Pressure Lines ] Service and Repair.
• Attach the balance weight, refer to => [ Positioning the Balance Weight ] Service and Repair.
6 Fuel Pressure Regulator Valve (N276)
• 80 Nm
• Checking, refer to => [ Fuel Pressure Regulator Valve, Checking ] Scan Tool Testing and Procedures.
• Removing and installing, refer to => [ Fuel Pressure Regulator Valve N276 ] Service and Repair.
7 Fuel Rail (High Pressure Reservoir)
8 Fuel Temperature Sensor (G81)
9 Fuel Supply Line
• Make sure it is secure.
• Between the fuel temperature sensor and the high pressure pump.
10 High Pressure Pump
• Removing and installing, refer to => [ High Pressure Pump ] High Pressure Pump.
• Tightening specification for the toothed belt drive, refer to => [ Toothed Belt Overview ] Toothed Belt Overview.
11 Bolt
• 20 Nm
• Always replace.
• Tighten the long bolts + an additional 180° (1/2) turn.
• Tighten the short bolts + an additional 45° (1/8) turn.
12 Bracket
• For the fuel temperature sensor
13 Fuel Supply Line
• White or with a white mark.
• Make sure it is secure.
• From the auxiliary fuel pump or fuel pump 2.
14 Fuel Pressure Sensor (G247)
• 100 Nm
• Removing and installing, refer to => [ Fuel Pressure Sensor G247 ] Service and Repair.
15 Bolt
• 22 Nm
16 Tensioning Plate
• Always replace.
• Note the installed position, refer to => [ Tensioning Plate Installed Position ].
17 Nut
• 10 Nm
18 Sealing Cap
19 Bolt
• 5 Nm
20 Fuel Injector (Piezo Injector)
• Removing and installing, refer to => [ Fuel Injectors ] Service and Repair.
• The following parts, seals or O-rings must be replaced during each removal or installation, or when a fuel injector is being replaced: "Copper washer", "injector shaft O-ring", "injector return O-ring"
• Install any removed injectors back into their original location (cylinder).
• Visually check the sealing cones before using the "high pressure line" again.
• Check the sealing cone on each high pressure line for damage and deformation.
• The bore in the line must not be deformed or narrowed.
• Do not use corroded lines again.
21 High Pressure Lines
• 28 Nm
• Between the high pressure pump and the fuel rail.
Tensioning Plate Installed Position
Fuel Return Line Differences
- A -, No ribbing, connect the overflow fuel line clamp per the Parts Catalog.
- B -, With ribbing, DO NOT use a clamp to connect the overflow fuel line.
Connection: High Pressure Line between the High Pressure Pump and the Fuel Rail
