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Checking fuel delivery rate > < Checking fuel pressure

Polo Mk5

Checking holding pressure
Checking holding pressure
   
l  Fuel pressure OK and pressure tester -VAS 6550- connected. Check fuel pressure → Chapter.
Test sequence:
–  Actuate fuel pump with final control diagnosis to build up fuel pressure.
–  Read fuel pressure on pressure gauge.
l  Specification: 4.0…7.0 bar
–  Watch pressure drop on pressure gauge. After 10 minutes, pressure must not drop below 3.0 bar.
If the pressure drops further:
–  Actuate fuel pump with final control diagnosis to build up fuel pressure.
  N20-10628
–  After pressure has built up, close cut-off tap -B- of pressure tester immediately. Lever is then at right angle to direction of flow.
If the pressure does not drop now:
  Note
Search for leak on engine side. Repeat holding pressure test. This time, close shut-off tap -A- to check whether leak actually is on engine side.
–  Check fuel pipe to high-pressure pump for leaks.
If no fault is found:
–  Replace high-pressure pump → Fuel preparation, injection; Rep. gr.24.
If the pressure drops again:
Leak must be sought on fuel tank side; proceed as follows:
–  Check fuel supply line to fuel filter for leaks.
If no fault is found on the fuel line:
–  Check pressure retention valve in fuel delivery unit. Proceed as follows:
  N20-10598
–  Pull fuel supply line -arrow- off fuel filter. Detach push-on connectors → Chapter
  N20-10629
–  Connect pressure tester -VAS 6550- between fuel filter and fuel supply line with adapter -VAS 6550/1- and -VAS 6550/2-.
–  Make sure that drain tap is closed and cut-off taps are open.
–  Actuate fuel pump with final control diagnosis to build up fuel pressure.
–  Read fuel pressure on pressure gauge.
l  Specification: 4.0…7.0 bar
  N20-10630
–  After pressure has built up, close cut-off tap -A-.
–  Watch pressure drop on pressure gauge. After 10 minutes, pressure must not drop below 3.0 bar.
If pressure drops:
–  Pressure retention valve in fuel pump defective; renew fuel delivery unit → Chapter.
If the pressure does not drop:
–  Pressure retention valve in fuel filter is OK, pressure limiting valve in fuel filter is defective. Renew fuel filter.
  N20-10598

Checking fuel delivery rate > < Checking fuel pressure