Fuel System Overview, Diesel
Fuel System Overview
• Follow the guidelines for a clean working environment when working on the fuel system. Refer to => [ Fuel System ] Fuel System.
• Always follow these rules before and during work.
Follow the points below to avoid running the high pressure fuel pump dry (very low tolerances) and to start the engine quickly after replacing the components:
• If fuel system components between the fuel tank and high pressure fuel pump are removed or replaced, then a fuel first filling must be performed.
• It is necessary to bleed the fuel system before starting the engine for the first time if the fuel pump, the fuel line (between the fuel tank and the fuel high pressure pump) or the fuel filter were removed.
• If the fuel high pressure pump was removed or replaced, then bleed the fuel system before starting the engine for the first time.
Filling the fuel for the first time, refer to => [ Fuel System, Filling and Bleeding ] Fuel System, Filling and Bleeding.
• Not paying attention to the first filling will damaged the fuel high pressure pump.
1 Bolt
• 10 Nm
2 High-Pressure Line
• 25 Nm
• Between the high pressure pump and fuel rail
3 Fuel Return Lines
• To fuel tank
• The fuel return line must not be bent, damaged or plugged
• Do not disassemble the fuel return lines. Replace them completely with the pressure retention valve.
• The check valve always maintains a residual pressure (control quantity) of approximately 10 bar in the fuel return lines.
• The fuel injectors require this control quantity to function correctly.
• Check pressure retaining valve, refer to => [ Pressure Retention Valve in Fuel Return Line, Checking ] Pressure Retention Valve In Fuel Return Line, Checking
• 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.
4 Bolt
• 10 Nm
5 High-Pressure Lines
• 25 Nm
• Between the fuel rail and fuel injectors
• Do not interchange
• Install without tension
• When using the high pressure line again, pay attention to the cylinder marking.
• The high pressure lines can be reused only after the following checks:
• Check the sealing cone on each high pressure line for deformation and cracks.
• The bores for the lines must not be deformed, narrowed or damaged.
• Do not use corroded lines again.
6 Fuel Pressure Regulator Valve (N276)
• 80 Nm
• Cannot be used again
• Removing and installing, refer to => [ Fuel Pressure Regulator Valve (N276) ] Service and Repair
7 Fuel Rail
• Removing and installing, refer to => [ Fuel Rail ] Service and Repair
8 Fuel Supply Line
9 Fuel High Pressure Pump
• With fuel metering valve (N290) not opened
• Removing and installing, refer to => [ High Pressure Pump ] High Pressure Pump
10 Bolt
• 20 Nm
• Tighten the long bolts an additional 180°
• Tighten the short bolts an additional 90°
11 Bolt
• 20 Nm
12 Toothed Belt Gear for the High Pressure Pump
13 Nut
• 95 Nm
14 Hub
• With sensor ring
• Use camshaft gear counter-holder (T10051) to loosen and tighten
• Use the ignition coil puller (T40064) to remove.
15 Fuel Pressure Sensor (G247)
• 100 Nm
• Removing and installing, refer to => [ Fuel Pressure Sensor (G247) ] Fuel Pressure Sensor (G247)
16 Bolt
• 22 Nm
17 Tensioning Bracket
• Injectors and tensioning brackets that have been removed and are being reinstalled may only be installed in the same cylinder.
• If the injector unit is being replaced, then the tension bracket must also be replaced.
18 Hex Shoulder Nut
• 10 Nm
• For the tension bracket
19 Injection Unit Cover
20 Bolt
• 5 Nm
21 Injector
• Install any removed injectors, high pressure lines and tensioning brackets in their original locations.
• Removing and installing, refer to => [ Fuel Injectors ] Removal and Replacement
Tensioning Bracket Installation Position
