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Checking non-return valve for fuel pump > < 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.
  WARNING
Fuel system is under pressure! Before opening the system place a cloth around the connection. Then release pressure by carefully loosening the connection.
   
–  Pull off supply line -1- and catch escaping fuel with a cloth.
  Note
Press in securing ring to release fuel lines.
  A10-0140
–  Connect K-Jetronic pressure tester -V.A.G 1318- with double union -V.A.G 1318/23- and adapter set -V.A.G 1318/17- to fuel supply line.
–  Push hose adapter -V.A.G 1318/16- onto adapter -V.A.G 1318/11- of pressure gauge and hold it in 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 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 delivery rate of the fuel pump depends on the battery voltage. Therefore connect the multimeter with auxiliary cables from auxiliary measuring set -V.A.G 1594A- or auxiliary measuring set -V.A.G 1594C- to the vehicle battery.
–  Operate remote control -V.A.G 1348/3A- of V.A.G 1348 for 30 seconds while measuring battery voltage.
  N20-0470
–  Compare quantity of fuel delivered with specification.
*) Minimum delivery rate 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 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 line -1- off inlet to fuel filter.
–  Connect K-Jetronic 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 → Chapter.
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 road test, but a 2nd person is necessary.
If current draw is exceeded:
–  Renew fuel delivery unit → Chapter.
  N20-0075

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