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Home >> Audi >> 2009 >> Q7 4.2 >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 23 (3.0L - Diesel Fuel Injection - Engine Code: CATA) >> 23 Diesel Fuel Injection >> Overview - Fuel System

Overview - Fuel System

WARNING: This page is about a different variant/trim than selected.
WARNING:
CAUTION:

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 were removed or replaced, the fuel system must be bled. Refer to FUEL SYSTEM BLEEDING .
  • 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 high pressure fuel pump) or the fuel filter were removed.
  • If the high pressure fuel pump was removed or replaced, then bleed the fuel system before starting the engine for the first time.

Fill the fuel tank after installing the high pressure pump. Refer to FUEL TANK, FILLING WITH FUEL AFTER INSTALLING HIGH PRESSURE PUMP .

Fig 1: Identifying Fuel System Overview
GWWA23-10288Courtesy of AUDI OF AMERICA, LLC
  1. Fuel Return Line
    • To the fuel tank
    • The fuel return line must not be bent, damaged or plugged
  2. Fuel Supply Line
    • Coming from the fuel filter
  3. Fuel Return Line Banjo Fitting
    • 25 Nm
  4. Fuel Temperature Sensor -G81-
  5. Bolt
  6. Bracket
  7. Fuel Pressure Regulator Valve -N276-
    • Installed on cylinder bank 1
    • Cannot be used again
    • The adaptation values must be adapted after replacing the high pressure pump or the Fuel Pressure Regulator Valve -N276-. Refer to "Guided Functions" using the Vehicle Diagnostic Tester.
    • Removing and installing. Refer to Fuel Pressure Regulator Valve -N276-, REMOVING AND INSTALLING .
  8. Bolt
  9. Bracket
  10. High Pressure Fuel Line
    • Between the high pressure pump and fuel rail
  11. High Pressure Fuel Line
    • Between the cylinder bank 1 fuel rail and cylinder bank 2 fuel rail
    • Before reusing the "fuel high pressure line", check the sealing cones for damage such as scratches or corrosion. Replace if damaged.
    • If the high pressure line is not OK, always replace the high pressure line
  12. Fuel High Pressure Pump
  13. Fuel Return Lines
  14. Bolt
    • 5.5 Nm
    • Injector unit cover to cylinder head cover
  15. Injection Unit Cover
  16. Tension Clamp
    • Replace
  17. Hex Shoulder Nut
    • 10 Nm
    • For the tension clamp
  18. Bolt
    • 22 Nm
    • For the cylinder bank 2 fuel rail
  19. Fuel Pressure Sensor -G247-
  20. Seal
    • Replace
  21. Fuel High Pressure Lines
    • 25 Nm
    • For cylinder bank 2
  22. Fuel Rail
    • For cylinder bank 2
  23. Seals
    • Replace
  24. Hex Shoulder Nut
    • 10 Nm
    • For the tension clamp
  25. Injector
    • Mark fuel injector and high pressure lines with paint to each other and to the cylinder for reinstallation, when installing pay attention to the markings.
    • Replace the copper ring seal during every assembly/disassembly procedure.
    • To remove rust particles on the fuel injector sealing surface, clean the fuel injector shaft in the cylinder head using the Cleaning SetVAS6811 (always clean in the event of leaks).
    • Removing and installing. Refer to PIEZOELECTRIC FUEL INJECTORS, REMOVING AND INSTALLING .
  26. Bolt
    • 5.5 Nm
    • Injector unit cover to cylinder head cover
  27. Injection Unit Cover
  28. Seal
    • Replace
  29. Fuel High Pressure Lines
    • For cylinder bank 1
  30. Bolt
    • 22 Nm
    • For the cylinder bank 1 fuel rail
  31. Fuel Return Lines
  32. Pressure Retaining Valve or Restrictor
    • The type of component that was installed is dependent upon the model year
    • The check valve always maintains a residual pressure (control quantity) of approximately 10 bar (145 psi) in the fuel return lines.
    • The restrictor always maintains a residual pressure (control quantity) of approximately 4 bar (58 psi) in the fuel return lines.
    • The Piezoelectric injectors need this control quantity for their function.
    • The check valve or the restrictor can be replaced only with the complete fuel return lines.
    • Bleed the fuel system after replacing. Refer to FUEL TANK, FILLING WITH FUEL AFTER INSTALLING HIGH PRESSURE PUMP 
    • Check pressure retaining valve. Refer to FUEL RETURN CHECK VALVE, CHECKING 
    • Check the restrictor. Refer to RESTRICTOR IN THE FUEL RETURN LINE, CHECKING 
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