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Engine control unit > < Checking quantity injected

Golf Mk5

Checking fuel pressure regulator and holding pressure
Checking fuel pressure regulator and holding pressure
Special tools and workshop equipment required
   
t  Pressure gauge -VAS 6550-
  Note
t  The fuel pressure regulator regulates the fuel pressure to approx. 4 bar.
t  The fuel pressure regulator is located on the fuel filter. From October 2005, the fuel pressure regulator has been integrated in the fuel filter and cannot be renewed individually.
t  Always follow safety precautions → Chapter.
t  Observe rules for cleanliness → Chapter.
  WARNING
Fuel supply line is pressurised. Wear eye protection and protective clothing to avoid possible injury and skin contact. Before loosening hose connections, wrap a cloth around the connection. Then release pressure by carefully pulling hose off connection.
  W00-10774
–  Pull off supply line (metal coupling) -arrow- and catch escaping fuel with a cloth.
  Note
Press in securing ring to release fuel line.
  N20-10127
–  Connect pressure tester -VAS 6550- to 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.
–  Start engine and run at idling speed.
  Note
If engine does not start, activate fuel pump with final control diagnosis → Chapter.
–  Read fuel pressure on pressure gauge. Specification: 3.8…4.2 bar.
If fuel pressure is OK, check holding pressure → Anchor.
If the specification is exceeded:
–  Check fuel return line between fuel filter and flange for possible restrictions (kinks) or blockages.
If no fault is found:
–  Fuel pressure regulator defective, renew fuel pressure regulator and/or fuel filter.
If the specification is not attained:
–  Check fuel lines for possible restrictions (kinks) or blockages.
If no fault is found:
–  Renew fuel pressure regulator and/or fuel filter.
–  Repeat check.
If the specifications are still not attained:
–  Fuel pump defective, renew fuel delivery unit → Chapter.
If the specification is attained, check holding pressure.
Checking holding pressure
Prerequisites:
l  Fuel pressure on pressure gauge: 3.8 … 4.2 bar.
  N20-10628
–  Watch pressure drop on pressure gauge. After 10 minutes, pressure must not drop below 3.0 bar.
If the pressure drops further:
–  Start engine and run at idling speed.
  N20-10628
–  Switch off ignition and close shut-off tap -B- of pressure tester immediately.
If the pressure does not drop now:
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 rail and injectors for leaks.
If the pressure drops again:
(Leak - fuel tank side)
–  Check fuel lines for leaks.
If no fault can be found on the fuel lines:
–  Check fuel pump non-return valve → Chapter.
If no fault is found
–  Renew fuel pressure regulator and/or fuel filter.
When the pressure tester is removed after the test has been completed:
–  Switch off ignition.
–  Wrap a cloth around the joint to catch fuel which flows out.
  N20-10598

Engine control unit > < Checking quantity injected