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Lambda probe > < Checking fuel pressure senderG247

A3 Mk2

Checking fuel pressure and residual pressure (up to high-pressure pump)
Checking fuel pressure and residual pressure (up to high-pressure pump)
Special tools and workshop equipment required
   
t  Pressure tester -VAS 6550- with adapters -VAS 6550/1- and -VAS 6550/2-
t  Fuel-resistant measuring container
Test conditions
l  Battery voltage at least 12.5 V.
l  Fuel filter OK.
l  Fuel tank at least 1/4 full.
l  Fuel pump control unit -J538- OK (check)
l  Ignition off.
Test sequence
  WARNING
Fuel system is pressurised (initial fuel pressure). Wear safety goggles and protective clothing to avoid possible injury and skin contact. Wrap a cloth around the connection before opening the fuel system. Then dissipate residual pressure by carefully detaching the connection.
  W00-10774
–  Lift release tab and disconnect fuel supply line -arrow-.
  A24-10452
–  Connect pressure tester -VAS 6550- with adapters -VAS 6550/1- and -VAS 6550/2- to fuel supply line.
–  Make sure that drain tap (centre hose) is closed and cut-off valves (left and right) are open.
–  Switch on ignition.
–  Fuel pump will run for approx. 5 seconds and build up fuel pressure.
–  Read fuel pressure off pressure tester -VAS 6550-.
l  Specification: 4.0 ... 7.0 bar
If specification is not obtained:
–  Check delivery rate of fuel pump → Fuel supply system, petrol engines; Rep. gr.20.
Checking residual pressure
–  Check system for leaks and check residual pressure by watching the drop in pressure on the pressure tester -VAS 6550-.
l  After 10 minutes pressure should still be at least 3 bar.
If the residual pressure drops below 3 bar:
t  Check union between pressure tester -VAS 6550- and fuel supply line for leaks.
t  Check pressure tester -VAS 6550- for leaks.
t  Check fuel lines and their connections for leaks.
t  Renew fuel filter with integrated fuel pressure regulator → Fuel supply system, petrol engines; Rep. gr.20. Then repeat the test.
t  If fuel filter is OK, renew fuel pump → Fuel supply system, petrol engines; Rep. gr.20.
Assembly is carried out in the reverse order; note the following:
–  The ignition must be switched off.
  Note
  N20-10628
Before removing the pressure tester, release the fuel pressure by opening the drain tap (centre hose). Hold end of hose into a measuring container.
  N20-10628
–  Re-attach fuel supply line -arrow- (make sure that all parts are clean and that there are no leaks).
  A24-10452

Lambda probe > < Checking fuel pressure senderG247