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Bleeding fuel system > < System layout

A4 Mk3

Fuel system - exploded view
Fuel system - exploded view
  WARNING
t  Always read rules for cleanliness and instructions for working on fuel system → Chapter.
t  Follow these instructions and rules for cleanliness before starting work and while working on the fuel system.
  Caution
To prevent the high-pressure fuel pump from running while it is empty and to ensure that the engine starts quickly after parts have been renewed, it is important to observe the following:
t  If components of the fuel system between the fuel tank and the high-pressure fuel pump are removed or renewed, the first fuel filling must be performed.
t  If a fuel pump, fuel line (between fuel tank and high-pressure fuel pump) or fuel filter is removed or renewed, the fuel system must be bled before the engine is started for the first time.
t  If the high-pressure fuel pump is removed or renewed, the fuel system must be bled before the engine is started for the first time.
Procedure for first fuel filling → Chapter
  Note
The high-pressure pump will be damaged if the first fuel filling operation is not performed.
   
1 - Bolt
q   10 Nm
2 - High-pressure pipe
q   25 Nm
q   Between high-pressure pump and fuel rail
3 - Fuel return lines
q   To fuel tank
q   Fuel return line must not be kinked, damaged or clogged
q   The fuel return lines must not be dismantled; if necessary they must be renewed complete with pressure retention valve
q   The pressure retention valve maintains a residual pressure of approx. 10 bar in the return lines
q   This residual pressure is required for the control function of the injectors
q   Checking pressure retention valve → Chapter
q   After replacement, engine must be run at idling speed for approx. 2 minutes to bleed fuel system. Then check fuel return lines for leaks
4 - Bolt
q   10 Nm
5 - High-pressure pipes
q   25 Nm
q   Between fuel rail and injectors
q   Do not interchange
q   Install free of stress
6 - Fuel pressure regulating valve -N276-
q   80 Nm
q   Cannot be re-installed
q   Removing and installing → Chapter
7 - Fuel rail
q   Removing and installing → Chapter
8 - Fuel supply line
9 - High-pressure pump
q   With fuel metering valve -N290- (do not open)
q   After renewing, first fuel filling operation MUST be performed (it is important not to allow pump to run while it is still empty) → Chapter
q   Removing and installing → Chapter
10 - Bolt
q   20 Nm
q   Turn long bolts 180° further
q   Turn short bolts 90° further
11 - Bolt
q   20 Nm
12 - Toothed belt sprocket for high-pressure pump
13 - Nut
q   95 Nm
14 - Hub
q   With sender wheel
q   Use counterhold tool -T10051- to loosen and tighten
q   To remove, use puller -T40064-
15 - Fuel pressure sender -G247-
q   100 Nm
q   Removing and installing → Chapter
16 - Bolt
q   22 Nm
17 - Clamping piece
q   If they are to be re-installed, the injectors and clamping pieces must always be re-fitted on the same cylinder.
q   When an injector is renewed, the corresponding clamping piece must be renewed at the same time
18 - Hexagon flange nut
q   For clamping piece
q   10 Nm
19 - Cover for injector
20 - Bolt
q   5 Nm
21 - Injector
q   If they are to be re-installed, the injectors, high-pressure fuel pipes and clamping pieces must always be re-fitted in their original positions (i.e. on the same cylinder).
q   Removing and installing → Chapter

   
Installation position of clamping piece
  N23-10231

Bleeding fuel system > < System layout