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

Golf Mk4

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.
   
–  Pull off supply hose -1- (with white marking) and catch fuel that escapes with a cloth.
  Note
Press safety ring in to release fuel lines.
  WARNING
Fuel supply lines are under pressure! Wear protective glasses 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-.
–  Push hose adapter -V.A.G 1318/16- onto adapter -V.A.G 1318/11- of pressure tester -V.A.G 1318- and hold it in measuring container.
–  Open shut-off tap 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.
–  Empty measuring container.
–  The quantity delivered by the fuel pump depends on the battery voltage. Therefore connect multimeter -V.A.G 1715- with adapter cables from auxiliary measuring set -V.A.G 1594C- to vehicle battery.
–  Operate remote control for 30 seconds while measuring battery voltage.
  N20-0470
–  Compare quantity of fuel delivered with specification.
*) Minimum delivery rate cm3/30 seconds
**) 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 200 cm3/30 s.
If the minimum delivery rate is not attained:
–  Check fuel lines for possible restrictions (kinks) or blockages.
  N20-0169
–  Pull supply hose -1- off inlet to fuel filter.
–  Connect pressure tester -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 for dirt in filter strainer.
Only if still no fault has been detected:
–  Renew 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.
  N20-0471
–  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 test drive, but a 2nd person is necessary.
If current draw is exceeded:
–  Fuel pump is defective. Renew fuel delivery unit → Chapter.
  N20-0075

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