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Checking fuel pump non-return valve > < Checking delivery rate

Leon Mk2

Test sequence
Test sequence
–  Remove filler cap from fuel tank filler neck.
   
–  Pull fuel supply hose (white marking) off fuel supply pipe -1-.
  Caution
Fuel supply pipes are under pressure! Before removing from hose connection wrap a cloth around the connection. Then release pressure by carefully pulling hose off connection.
–  Connect pressure gauge -V.A.G 1318- with adapter /1 to fuel supply pipe.
–  Push the hose -V.A.G 1318/16- onto the adapter -V.A.G 1318/11- on the pressure gauge and hold hose in a measuring container.
–  Open shut-off tap on pressure gauge. The lever will indicate flow direction -A-.
–  Operate remote control -V.A.G 1348/3A-, slowly closing shut-off tap until pressure gauge indicates a pressure of 3 bar. At this point do not move shut-off tap any further.
–  Empty the measuring container.
–  The quantity of fuel delivered by the fuel pump is dependent upon battery voltage. Therefore connect the multimeter with adapter cables from -V.A.G 1594- to the vehicle battery.
–  Operate remote control for 30 seconds and measure battery voltage.
  E20-0089
–  Compare the quantity of fuel delivered with specification.
-*- Minimum delivery cm³/30 seconds
-**- Voltage at fuel pump with engine stationary and pump running (approx. 2 volts less than battery voltage).
Example:
During the test a voltage of 12.5 volts is measured at the battery. As the voltage at the pump is approx. 2 volts less than the battery voltage, this will equate to a minimum delivery of 540 cm³/30 s.
If the minimum delivery rate is not attained:
–  Check the fuel pipes for possible restrictions (kinks) or blockages.
  N20-0134
–  Pull supply hose -1- off inlet to fuel filter.
  Note!
Press buttons on hose couplings to do this.
–  Connect pressure gauge -V.A.G 1318- with adapter -1318/17- to fuel supply pipe.
–  Repeat delivery rate check.
If the minimum delivery rate is now attained:
–  Replace the fuel filter.
If the minimum delivery rate is again not attained:
–  Remove the fuel delivery unit and check the strainer filter for soiling.
Only when up to now no fault has been detected:
–  Fuel pump defective, renew fuel delivery unit → Chapter: Removing and installing fuel delivery unit.
If the delivery rate has been attained but nevertheless you suspect a fuel supply system fault (e.g. intermittent failure of fuel supply system):
–  Check the current draw of the fuel pump as follows:
–  Reconnect all disconnected fuel pipes.
  N20-0471
–  Connect the multimeter -V.A.G 1715- using the current clamp to the red/yellow wire from wiring harness.
–  Start the engine and run at idling speed.
–  Measure the current draw of the fuel pump. Specification: max. 8 amps.
  Note!
If the fuel system malfunction is intermittent, you can perform the check during a test drive with the help of a 2nd person.
If the current draw is exceeded:
–  Fuel pump defective, renew fuel delivery unit → Chapter: Removing and installing fuel delivery unit.
  N20-0061

Checking fuel pump non-return valve > < Checking delivery rate