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Intake manifold, air filter > < Check the fuel system for tightness

Octavia Mk2

Check the pressure holding valve in the fuel return-flow line
Check the pressure holding valve in the fuel return-flow line
The pressure holding valve in the fuel return-flow line has the function to always hold a remaining pressure (control quantity) of approx. 1 MPa (10 bar).
The injection units (piezo injectors) require this control quantity for their function.
Special tools and workshop equipment required
t  Pressure gauge, e.g. -VAS 6330-
t  Adapter, e.g. -V.A.G 1318/17A-
t  Cleaning and degreasing agent, e.g. -D 009 401 04-
t  Protective goggles and gloves
Test sequence
  Note
t  Observe safety measures when working on the fuel system → Chapter.
t  Observe rules for cleanliness → Chapter.
–  Remove engine cover → Chapter.
  WARNING
Wear protective gloves and protective googles when working with grease remover!
–  Before removing, clean the return line connection at the injection unit of cylinder 1 with a grease remover.
–  Dry the return line connection of cylinder 1.
–  Cover the return line connection of cylinder 1 with a cloth.
–  Remove the connection of the fuel return-flow line at cyl. 1, to do so pull the unlocking bolt upwards.
  Note
   
t  If the unlocking bolt of the connection for the fuel return-flow line cannot be pulled up by hand, slacken the bolt by turning it with a narrow screwdriver -arrows-.
t  Pay attention to cleanliness, no impurities must get into the open return lines and into the connections of the injection units.
  A23-10214
–  For example, connect the pressure gauge VAS -6330- between the return line connection at the injection unit and the return-flow line.
–  Open shut-off cock of the pressure gauge.
–  Start engine and run in idle.
–  Read the pressure on the pressure gaugeVAS -6330-.
l  Specified value: 0,8 ... 1,4 MPa (8 ... 14 bar)
If the specified value is not reached, the pressure holding valve is defective.
–  Completely replace the fuel return-flow line of the injection units.
  A23-10115

Intake manifold, air filter > < Check the fuel system for tightness