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Check fuel pressure and non-return valve > < Inspecting proper operation and power supply

Fabia Mk2

Check fuel flow rate
Check fuel flow rate
Test condition
l  Supply voltage o.k.
l  Remote control -V.A.G 1348/3A - connected.
Test sequence
–  Unscrew the cap from the filler neck.
   
–  Pull out the fuel feed line -2- and catch the fuel which flows out with a cleaning cloth.
  WARNING
The fuel feed line is pressurized! Place a clean cleaning cloth around the connection point before detaching hose connections. Reduce pressure by carefully releasing the connection point.
  S10-0389
–  Connect pressure gauge appliance -V.A.G 1318- with adapter -V.A.G 1318/23 - and -V.A.G 1318/17- to the fuel feed line.
–  Connect hose -V.A.G 1318/1- to adapter -V.A.G 1318/11- of the pressure gauge appliance and hold in the measuring vessel.
–  Open shut-off cock of the pressure measuring device. The lever points in the direction of flow -A-.
–  Activate remote control -V.A.G 1348/3A-. While doing this, slowly close the shut-off cock until the pressure gauge displays 3 bar (0.3 MPa) pressure. Now do not change the position of the shut-off cock.
–  Drain the measuring vessel.
–  The fuel flow rate of the fuel pump is dependent on the battery voltage. Therefore connect the multimeter with the adapter cable to the vehicle battery.
–  Activate the remote control for 30 seconds while measuring the battery voltage.
  N20-0132
–  Compare the fuel rate with the specified value.
*) Minimum flow rate in cm3/30 s
**) Voltage at fuel delivery unit when engine not running and delivery unit operating (approx. 2 volts less than battery voltage)
Read out examples:
During the test a voltage of 12.5 V was measured on the battery. As the voltage on the fuel delivery unit is approx. 2 V less than the battery voltage, a minimum flow rate of 540 cm3/30 s is shown in the diagram.
If the minimum flow rate is not reached:
–  Check the fuel lines for possible diameter restrictions (kinks) or blocking.
  S20-0204
–  Disconnect the hose -1- of the feed line from the fuel filter inlet.
–  Connect pressure gauge appliance -V.A.G 1318- with adapter -V.A.G 1318/17 - to the hose -1-.
–  Repeat fuel flow rate test.
If the minimum flow rate is now reached:
–  Replace fuel filter.
If the minimum flow rate is again not reached:
–  Remove the fuel delivery unit and check whether the pump strainer is not clogged up.
If no fault was detected until now:
–  Replace fuel delivery unit.
The fuel flow rate was reached but a fault in the fuel supply system is suspected (e.g. temporary failure of the fuel supply system):
–  Check the power consumption of the fuel delivery unit as follows:
–  Connect all released fuel lines.
  S20-0319
–  Connect multimeter with current probe on the line from contact -1- of the connector of the fuel delivery unit.
–  Start engine and run in idle.
–  Measure voltage consumption of the fuel pump.
Specified value: max. 8 A
  Note
If the failure in the fuel supply is occasional the test may be performed during a test drive. The assistance of a 2nd mechanic is required.
If the power consumption is exceeded:
–  Replace fuel delivery unit.
  S20-0298

Check fuel pressure and non-return valve > < Inspecting proper operation and power supply