Fuel System Overview
Fuel System Overview
CAUTION!
• Follow the guidelines for a clean working environment when working on the fuel system. Refer to => [ Clean Working Conditions and Fuel System Work Instructions ] Clean Working Conditions and Fuel System Work Instructions.
• Always follow these rules before and during work.
1 - Fuel Return Line
• To the fuel tank.
• The fuel return line must not be bent, damaged or plugged.
2 - Fuel Supply Line
• From the fuel filter.
3 - Fuel Return Line Banjo Bolt
4 - Fuel Temperature Sensor (G81)
5 - Bolt
6 - Bracket
7 - Fuel Pressure Regulator Valve (N276)
• Installed on cylinder bank 1.
• Cannot be reused.
• Removing and installing, refer to => [ Fuel Pressure Regulator Valve ] Service and Repair.
8 - Bolt
9 - Bracket
10 - High Pressure Fuel Line
• 28 Nm
• Between the high pressure pump and fuel rail.
11 - High Pressure Fuel Line
• 28 Nm
• Between the fuel rail cylinder bank 1 and fuel rail cylinder bank 2.
• Before reusing, check the sealing cones for damage, for example scratches or corrosion; always replace if damaged.
• If the high pressure line is not OK, always replace the high pressure line.
12 - High Pressure Fuel Pump
• With the fuel metering valve (N290).
• fill the fuel tank after replacing the high pressure fuel pump (never run dry). Refer to => [ Fuel System, Bleeding ] Fuel System, Bleeding.
• High pressure fuel pump overview. Refer to => [ High Pressure Fuel Pump Overview ] High Pressure Fuel Pump Overview.
• Removing and installing, refer to => [ High Pressure Fuel Pump ] High Pressure Fuel Pump.
13 - Fuel Return Lines (Leak Lines)
• Do not disassemble the fuel return lines. Replace them completely with the pressure retention valve.
• Run the engine at idle for approximately two minutes after replacing to bleed the fuel system and then check the fuel return lines for leaks.
14 - Bolt
• 5.5 Nm
• Injector unit cover to cylinder head cover.
15 - Injector Unit Cover
16 - Tensioning Bracket
• Injectors and tensioning brackets which have been removed and are being reinstalled may only be reinstalled into the same cylinder.
• If the fuel injector is being replaced, then the tension bracket must also be replaced.
17 - Nut
• 10 Nm
• For the tensioning bracket.
18 - Bolt
• 22 Nm
• For the cylinder bank 2 fuel rail.
19 - Fuel Pressure Sensor (G247)
• 30 Nm
• Installed in the fuel rail on cylinder bank 2.
• Removing and installing, refer to => [ Fuel Pressure Sensor ] Service and Repair.
20 - Seal
• Replace
21 - High Pressure Fuel Lines
• 28 Nm
• For cylinder bank 2.
22 - Fuel Rail (High Pressure Reservoir)
• For cylinder bank 2.
23 - Seals
• Replace
24 - Nut
• 10 Nm
• For the tension bracket.
25 - Fuel Injector (Piezo)
• The following components, seals and O-rings must be replaced each time a fuel injector is removed, and installed or replaced: "copper washer", "O-ring for the fuel injector shaft" and the "O-ring for the fuel injector return"
• The following components and seals and/or O-rings must be replaced whenever an injector is replaced:"tensioning bracket" "copper washer" "injector shaft O-ring" "injector return O-ring"
• Before reusing the injector high pressure line check the sealing cones for damage, for example scratches or corrosion; always replace if damaged.
• If any fuel injectors, injector high pressure lines and tensioning brackets, which were removed, are being reinstalled, then they must be reinstalled on the same cylinder.
• Removing and installing, refer to => [ Fuel Injectors ] Service and Repair.
26 - Bolt
• 5.5 Nm
• Injector unit cover to cylinder head cover.
27 - Injection Unit Cover
28 - Seal
• Replace
29 - High Pressure Fuel Lines
• 28 Nm
• For cylinder bank 1
30 - Bolt
• 22 Nm
• For the cylinder bank 1 fuel rail.
31 - Fuel Return Lines (Leak Lines)
• Do not disassemble the fuel return lines. Replace them completely with the pressure retention valve.
• Run the engine at idle for approximately two minutes after replacing to bleed the fuel system and then check the fuel return lines for leaks.
32 - Pressure Retention Valve
• In the return lines from cylinder banks 1 and 2.
• The check valve always maintains a residual pressure (control quantity) of approximately 10 bar in the fuel return lines.
• The fuel injectors need this control quantity to function correctly.
• The check valve can be replaced only with the complete fuel return line.
• The engine must run at idle for approximately two minutes after replacing to bleed the fuel system.
• Checking, refer to => [ Fuel Return Check Valve, Checking ] Testing and Inspection.