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Fuel system - exploded view > < Overview of fitting locations

A4 Mk3

System layout
System layout
  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 - High-pressure fuel pump
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
2 - Fuel metering valve -N290-
q   Do not unscrew
3 - Filter strainer
4 - Fuel temperature sender -G81-
5 - Fuel pressure sender -G247-
q   100 Nm
q   Removing and installing → Chapter
6 - Fuel rail
7 - Fuel pressure regulating valve -N276-
q   80 Nm
q   Cannot be re-installed
q   Removing and installing → Chapter
8 - Injectors
q   Removing and installing → Chapter
9 - Fuel return lines
q   The fuel return lines must not be dismantled; if necessary they must be renewed complete with pressure retention valve
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
10 - 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   The pressure retention valve may only be renewed together with the fuel return lines
q   After replacement, engine must be run at idling speed for approx. 2 minutes to bleed fuel system
q   Checking pressure retention valve → Chapter
11 - Fuel cooler
q   Fitted on underbody
12 - Fuel tank
q   With fuel system pressurisation pump -G6-
13 - Preheating valve
14 - Supplementary fuel pump -V393-
15 - Fuel filter
q   Fuel filter - exploded view → Rep. gr.20
q   Renewing fuel filter → Rep. gr.20

   

Fuel system - exploded view > < Overview of fitting locations