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Accelerator control > < Removing and installing the tandem pump (Superb II, Octavia II, Fabia II, Roomster)

Octavia Mk2

Inspecting tandem pump (Superb II, Octavia II, Fabia II, Roomster)
Inspecting tandem pump (Superb II, Octavia II, Fabia II, Roomster)
Special tools and workshop equipment required
t  Tandem pump testing device -VAS 5187-
t  Pliers for spring strap clamps
t  Hose clamp -MP7-602 (3094)-
Test conditions
l  The coolant temperature must be at least 85°C.
l  Unit injectors O.K.
l  Fuel filter and fuel line must not be blocked.
Work procedure
  Note
t  Safety precautions when working on the fuel supply system → Chapter.
t  Observe the regulations concerning cleanliness when working on the fuel supply/injection system → Chapter.
   
–  Unplug connector -2- from the air mass meter -G70-.
–  Detach ventilation hose -1-, intake hose -3- and air guide -5-.
–  Release screw -4- and remove air filter.
  S10-0304
–  Release screw plug -arrow-.
  S20-0188
–  Connect pressure gauge appliance -VAS 5187- as shown.
–  Start engine and run in idle.
–  Note the pressure shown on the pressure gauge. Specified value: at least 3.5 bar (0.35 MPa).
–  Engine speed must increase to 4000 rpm.
–  Note the pressure shown on the pressure gauge. Specified value: at least 7.5 bar (0.75 MPa).
If the nominal value of min. 7.5 bar (0.75 MPa) is not reached:
–  Close return-flow line between tandem pump and fuel filter with hose clamp -MP7-602 (3094)-.
–  Start engine and engine speed must increase to 4000 rpm.
–  Note the pressure shown on the pressure gauge. Specified value: min. 0.75 MPa (7.5 bar).
If the specified value is reached:
Pressure loss at the unit injectors.
–  Replace O-rings for unit injectors.
If the specified value is still not reached:
–  Replace tandem pump → Chapter.
  Note
After removing the pressure gauge appliance tighten the plug to 25 Nm. Always replace the gasket ring.
Check tightness (internally) of tandem pump
  Note
After re-installing a used tandem pump e.g. after changing or repairing a cylinder head and/or after changing a hopper motor the tandem pump must absolutely be checked for internal tightness between fuel and oil side. In case of leakage the fuel penetrates into the engine oil, which can cause severe engine damage.
Special tools and workshop equipment required
t  Tester -V.A.G 1687-
Work procedure
–  Disconnect the fuel feed hose (white marking) and the fuel return hose (blue marking) from the tandem pump.
–  Close fuel return-flow connection at tandem pump with a dummy plug. Secure the dummy plug with a spring strap clamp.
Prepare tester -V.A.G 1687- as follows:
  Note
The rotary knob must be slightly pulled to the top in order to rotate the pressure control valve -2-.
  S20-0221
–  Unscrew pressure control valve -2- fully and close the valves -3- and -4-.
–  Connect hose with compressed air -1- (compressed air supply) to tester -V.A.G 1687-.
  Note
If there is water in the transparent water drain reservoir, drain water via the drain plug -6-.
–  Connect tester -5- with a commercially available connection for compressed air und a piece of fuel hose to the fuel feed connection of the tandem pump. To secure use a spring strap clamp.
–  Open valve -3-.
–  Set the pressure to 1.0 bar (0.1 MPa) with the pressure control valve -2-.
  WARNING
The maximum test pressure is 1.3 bar (0.13 MPa) and must not be exceeded.
  V21-0168
–  Open valve -4- and wait until the test circuit is filled. If necessary regulate the pressure to 1.0 bar (0.1 MPa).
–  Close the valve -3- to maintain the pressure and observe the drop in pressure over a period of 1 minute.
If no drop in pressure is detected, the tandem pump can be used again.
In case of drop in pressure:
–  Replace tandem pump → Chapter.
  V21-0168

Accelerator control > < Removing and installing the tandem pump (Superb II, Octavia II, Fabia II, Roomster)