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Fuel system pressure and holding pressure checking > < Functioning and voltage supply checking

Leon Mk2

Delivery rate checking
Delivery rate checking
Checking conditions
l  Fuel pump voltage supply O.K.
l  Remote control -V.A.G 1348/3A-, connected.
l  The delivery rate is checked at 3 bar. Therefore, the fuel pressure must be checked before measuring the delivery rate → Chapter, checking fuel pressure regulator and holding pressure.
Test sequence
–  Remove fuel filler cap.
   
–  Remove fuel return pipe -1-, press buttons on hose couplings to do this
–  Connect adaptor -V.A.G 1318/17- to pressure regulator and place the end of the pressure regulator in a measuring container.
  WARNING
Fuel supply hoses are under pressure. Before removing fuel hose connections, wrap a cloth around the connection. Then release pressure by carefully removing the hose.
–  Operate the remote control -V.A.G 1348/3A- for 5 seconds, to fill the fuel filter.
–  Empty the measuring container.
–  The quantity of fuel delivered by the fuel pump is dependent upon battery voltage. To do this, connect the multimeter with adapter cables from -V.A.G 1594 A- or -V.A.G 1594 C- to the vehicle battery.
–  Operate remote control -V.A.G 1348/3A- for 30 seconds and measure battery voltage.
  N20-0526
–  Compare the quantity of fuel delivered with specification.
*) Minimum delivery cm3/30 seconds
**)Voltage in fuel pump with engine off and the pump working (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 c.c./30 s.
If the minimum delivery rate is not attained:
–  Check the fuel pipes to the filter for possible restrictions (kinks) or blockages.
If the fuel pipes are O.K.:
–  Check the fuel delivery before the filter.
  N20-0134
–  Pull off supply pipe/hose -1- off inlet to fuel filter, press buttons on hose couplings to do this.
  WARNING
Fuel supply hoses are under pressure. Before removing fuel hose connections, wrap a cloth around the connection. Then release pressure by carefully removing the hose.
–  Connect pressure gauge -V.A.G 1318- with adapter -V.A.G 1318/17- to fuel supply pipe.
–  Connect adaptor -V.A.G 1318/11- and -V.A.G 1318/1- to the pressure gauge and place the end of the pressure regulator in a measuring container.
–  Open cut-off tap on pressure gauge. The lever points in direction of flow -A-.
–  Operate remote control -V.A.G 1348/3A- and slowly close cut-off tap, until pressure gauge shows a reading of approx. 3 bar. From this point on do not move position of cut-off tap.
–  Empty the measuring container.
–  The quantity of fuel delivered by the fuel pump is dependent upon battery voltage. To do this, connect the multimeter with adapter cables from -V.A.G 1594 A- or -V.A.G 1594 C- to the vehicle battery.
–  Operate remote control -V.A.G 1348/3A- for 30 seconds and measure battery voltage.
  N20-0531
–  Re-check the delivery rate and compare the quantity supplied with the value established in the first measurement.
If the minimum delivery rate is now attained:
–  Replace the fuel filter → Chapter.
If the minimum delivery rate is again not attained:
–  Remove the fuel delivery unit, and check the strainer in the unit for dirt.
Only up to the point that no fault has been detected:
–  Replace fuel supply unit → Chapter.
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.
  N20-0134
–  By means of the current clamp, connect multimeter -V.A.G 1715- to one of the fuel pump supply cables (external contacts of the flange connector).
–  Start the engine and run at idling speed.
–  Check the current draw of the fuel pump.
   Specification: 8 amperes max.
  Note
If the fuel system malfunction is intermittent, perform the check during a test drive with the assistance of a second person.
If the current draw is exceeded:
–  Replace fuel supply unit → Chapter.
  N20-0402

Fuel system pressure and holding pressure checking > < Functioning and voltage supply checking