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Checking fuel delivery rate (engine code BYT, BZB) > < Check the fuel pressure when driving (engine codes CCZB, CDAA)

Leon Mk2

Retention pressure: check
Retention pressure: check
   
l  Fuel pressure is correct and the pressure gauge -VAS 6550- connected. Check the fuel pressure → Chapter.
Checking process:
–  Actuate fuel pump with final control diagnosis to build up fuel pressure.
–  Take the fuel pressure reading on the pressure gauge. Specification: 4.0 - 7.0 bar
–  Watch pressure drop on pressure gauge. After 10 minutes the 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. The lever must point horizontally in the flow direction.
If the pressure does not drop any more:
  Note
Search for the leak on the engine side. Repeat the pressure retention test. This time, close the shut-off cock -A- to check if there is actually a leak on the engine side.
–  Check fuel pipe leading to high-pressure pump for leaks.
If no fault is found:
–  Replace the high-pressure pump → Chapter.
If the pressure drops again:
The leak must be detected from the side of the fuel tank. Proceed as follows:
–  Check the fuel pipe leading to fuel filter for leaks.
If no fault in fuel piping is detected:
–  Check pressure retention valve in fuel delivery unit. Proceed as follows:
  N20-10598
–  Pull fuel supply line -arrow- off fuel filter.
  N20-10629
–  Connect pressure tester -VAS 6550- between fuel filter and fuel supply line with adapter -VAS 6550/1- and -VAS 6550/2-.
–  Open cut-off tap on pressure gauge. Lever must point in direction of flow.
–  Turn the ignition on as many times as necessary until the fuel pressure on the pressure gauge does not increase any further.
–  Take the fuel pressure reading on the pressure gauge. Specification: 4.0…7.0 bar
  N20-10630
–  After pressure has been built up, close the shut-off cock -A-.
–  Watch pressure drop on pressure gauge. After 10 minutes the pressure must not drop below 3.0 bar.
If the pressure drops:
–  Fuel pump non-return valve is faulty, replace the fuel supply unit → Chapter.
If the pressure does not drop:
–  Pressure limiting valve in the fuel filter faulty: Replace the fuel filter.
  N20-10598

Checking fuel delivery rate (engine code BYT, BZB) > < Check the fuel pressure when driving (engine codes CCZB, CDAA)