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Fuel system - exploded view > < Overview of fitting locations

A3 Mk2

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
The high-pressure fuel pump has very close tolerances and must not be allowed to run without fuel. To prevent this and to enable the engine to start 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 procedure is not performed.
   
1 - Fuel tank
q   With fuel system pressurisation pump -G6-
2 - Fuel filter
q   Fuel filter - exploded view → Rep. gr.20
q   Renewing fuel filter → Rep. gr.20
3 - Supplementary fuel pump -V393-
4 - Filter strainer
5 - Fuel temperature sender -G81-
6 - High-pressure 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
7 - Fuel metering valve -N290-
q   Do not unscrew
8 - Fuel pressure regulating valve -N276-
q   80 Nm
q   Cannot be re-installed
q   Removing and installing → Chapter
9 - Fuel rail
10 - Fuel pressure sender -G247-
q   100 Nm
q   Removing and installing → Chapter
11 - 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
12 - Injectors
q   Injector, cylinder 1 -N30-
q   Injector, cylinder 2 -N31-
q   Injector, cylinder 3 -N32-
q   Injector, cylinder 4 -N33-
q   Removing and installing → Chapter

   

Fuel system - exploded view > < Overview of fitting locations