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Checking non-return valve for fuel pump > < Checking function and voltage supply

Golf Mk4

Checking fuel delivery rate
Checking fuel 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.
   
–  Pull off supply hose -1- (white marking) and catch fuel that escapes with a cloth.
  Note
Press buttons on hose couplings to do this.
  WARNING
Fuel supply lines are under pressure! Wear eye protection and gloves to avoid injuries and skin contact. Before loosening hose connections, wrap a cloth around the connection. Then release pressure by carefully pulling hose off connection.
  A10-0140
–  Connect pressure tester -V.A.G 1318- with connector -V.A.G 1318/23- and adapter set -V.A.G 1318/17- to fuel supply line
–  Push adapter -V.A.G 1318/1- onto adapter -V.A.G 1318/11- of pressure tester -V.A.G 1318- and hold it in measuring container.
–  Open shut-off valve of pressure tester -V.A.G 1318-. 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 shut-off tap until a pressure of 3 bar is displayed on pressure gauge. From this point on do not move position of shut-off tap.
–  Drain measuring container.
–  The fuel delivery rate of the fuel pump depends on the battery voltage. Therefore connect the multimeter -V.A.G 1715- with auxiliary cables from auxiliary measuring set -V.A.G 1594C- to the vehicle battery.
–  Operate remote control for 30 seconds while measuring battery voltage.
  N20-0109
–  Compare quantity of fuel delivered with specification.
-*)- Minimum delivery volume cm3/30 s
-**)- Voltage at fuel pump with engine not running 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 rate of 540 cm3/30 s.
If the minimum delivery rate is not attained:
–  Check fuel lines for possible restrictions (kinks) or blockages.
  N20-0134
–  Pull supply hose -1- off fuel filter inlet.
–  Connect pressure gauge -V.A.G 1318- with adapter set -V.A.G 1318/17- 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 filter strainer for soiling.
Only if still no fault has been detected:
–  Renew fuel delivery unit.
If fuel 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.
  N20-0242
–  Connect multimeter -V.A.G 1715- using pick-up clamp to the green/yellow wire in wiring harness.
–  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 current draw is exceeded:
–  Fuel pump defective, renew fuel delivery unit → Chapter.
  N20-0075

Checking non-return valve for fuel pump > < Checking function and voltage supply