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Check the retaining valve of the fuel pump > < Check the flow

Leon Mk2

Check procedure
Check procedure
–  Remove the fuel cap.
  Caution
The fuel advance conduit is under pressure. Before disconnecting the hoses, wrap a rag around the connection point. Then reduce pressure cautiously removing the hose.
   
–  Disconnect the fuel advance hose (with white mark) from the advance conduit -1-.
–  Connect the pressure measurement device -V.A.G. 1318- with the adaptor 1 to the advance conduit.
–  Screw the adaptor hose 13 together with the adaptor 7 to the measurement device and maintain in a measuring flask.
–  Open the pressure measurement device flow lock. The lever is pointed in the direction of the flow -A-.
–  Activate the remote control -V.A.G. 1348/3A-. Slowly close the flow until the manometer displays an overpressure of 3 bar. The flow position should not be modified now.
–  Empty the measuring flask.
–  The flow from the fuel pump depends on the voltage from the battery. Then connect the multimeter with auxiliary -V.A.G. 1594- equipment conduits to the vehicle battery.
–  Activate the remote control for 30 seconds and measure the battery voltage.
  N20-0117
–  Compare the quantity of fuel with the theoretical value.
-*- Minimum flow cm³/30 s
-**- Tension in the fuel pump with the motor off and the pump running (approx. 2 volts less than the battery).
Reading example:
During the check a battery tension of 12.5 volts is measured. Since the tension in the pump is approximately 2 volts lower than that of the battery, the result is a minimum flow of 540 cm³/30s.
If the minimum flow is not reached:
–  Check the fuel line for strangulations (foldings) or if there is blockage.
  N20-0134
–  Disconnect the advance conduit -1- from the fuel entry filter.
–  Connect the pressure measuring device -V.A.G. 1318- with the adaptor -V.A.G. 1318- 17 to the fuel advance line.
–  Repeat the flow check.
If the minimum flow is not now reached:
–  Replace the fuel filter.
If the minimum flow is not reached again:
–  Disassemble the fuel transport unit and check if the filtering cribble is dirty.
Only if until now no fault has been detected:
–  Replace the fuel transport unit.
Despite having reached the expected flow, there is suspicion of a failure in the fuel supply (i.e. temporary supply cut-off):
–  Check the current consumption of the fuel pump as follows:
–  Connect all of the disconnected fuel conduits again.
  N20-0242
–  Connect the multimeter -V.A.G. 1715- with pliers to the red/yellow cable in the cabling harness.
–  Start up the engine and allow it o idle.
–  Measure the current consumption of the fuel pump. Theoretical value: max. 8 amperes
  Note!
If it is a temporary failure in the fuel line, the check can be made during a test run. A second person will be needed for this procedure, however.
If the current consumption is exceeded:
–  Replace the fuel transport unit.
  N20-0061

Check the retaining valve of the fuel pump > < Check the flow