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

Leon Mk2

Checking delivery rate
Checking delivery rate
Test prerequisites
l  Voltage supply OK.
l  Remote control for V.A.G 1348 -V.A.G 1348/3A- is connected.
Test procedure
–  Remove filler cap from fuel tank filler neck.
–  Remove air filter → Rep. Gr.24
   
–  Pull off supply line -arrow- at fuel rail supply pipe and catch escaping fuel with a cleaning cloth.
  WARNING
Fuel system is under pressure! Before opening the system place a cloth around the connection. Then release pressure by carefully loosening the connection.
  N20-0426
–  Connect K-Jetronic pressure tester -V.A.G 1318- with adapter set -V.A.G 1318/10-12- to fuel supply line.
–  Connect hose adapter -V.A.G 1318/16- to adapter -V.A.G 1318/11- of K-Jetronic pressure tester -V.A.G 1318- and hold it in a measuring container.
–  Open the pressure tester shut-off tap. The lever then points in direction of flow -A-.
–  Operate remote control for V.A.G 1348 -V.A.G 1348/3A-. Then slowly close cut-off tap until a pressure of 3 bar is displayed on pressure gauge. From this point on do not move position of cut-off tap.
–  Empty measuring container.
–  The quantity delivered by the fuel pump depends on the battery voltage. Therefore connect multimeter to vehicle battery using adapter cables from auxiliary measuring set -V.A.G 1594 A- or auxiliary measuring set -V.A.G 1594C-.
–  Operate remote control -V.A.G 1348/3A- of V.A.G 1348 for 30 seconds while measuring battery voltage.
  N20-0427
–  Compare quantity of fuel delivered with specification.
-*- Minimum delivery cm3/30 s
-**- Voltage at fuel pump with engine stationary and pump running (approx. 2 volts less than battery voltage).
Example:
During the test a voltage of 12.2 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 rate of 550 cm3/30 s.
If the minimum delivery rate is not attained:
–  Check the fuel pipes for possible restrictions (kinks) or blockages.
  N20-0074
–  Pull supply hose -1- off inlet to fuel filter.
–  Connect K-Jetronic pressure tester -V.A.G 1318- with adapter set -V.A.G 1318/10-12- to hose.
–  Repeat delivery rate check.
If the minimum delivery rate is now attained:
–  Renew fuel filter.
If the minimum delivery rate is again not attained:
–  Remove fuel delivery unit and check for dirt in filter strainer.
Only if still no fault has been detected:
–  Fuel pump defective. Renew fuel delivery unit → Chapter, Removing and installing fuel delivery unit.
If delivery rate has been attained, but nevertheless you suspect a fuel supply system fault (e.g. intermittent failure of fuel supply system):
–  Check current draw of fuel pump as follows:
–  Reconnect all disconnected fuel lines.
  N20-0311
–  Connect multimeter -V.A.G 1715- with pick-up clamp to wire of wiring harness 4-pin connector -contact 1, arrow-.
–  Start engine and run at idling speed.
–  Measure current draw of fuel pump. Specification: max. 8 amps.
  Note
If the fuel system malfunction is intermittent, you can perform the check during a road test, but a 2nd person is necessary.
If the current consumption is exceeded:
–  Fuel pump defective. Renew fuel delivery unit → Chapter, Removing and installing fuel delivery unit.
  N20-0075

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