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Checking return flow rate of injectors at starter cranking speed > < Performing adaption of injector delivery calibration values

A1

Checking return flow rate of injectors with engine running
Checking return flow rate of injectors with engine running
A - Checking return flow rate of all injectors
Special tools and workshop equipment required
t  Fuel-resistant measuring container
  Caution
Risk of malfunctions caused by dirt.
Observe → Chapter „Rules for cleanliness and instructions for working on fuel system“.
–  Pull off engine cover panel → Chapter.
–  Disconnect hose connection at fuel line.
   
–  Seal off the open return connection with a plug -1-.
–  Hold end of fuel return hose -2- (lengthen if necessary) in a measuring container to measure the total return flow rate.
–  Start engine and let it idle for 2 minutes.
l  Specification for 2 minutes: 0 ml to 50 ml
–  If specification is attained, increase engine speed to 2000 ... 2500 rpm for approx. 2 minutes and then check return flow rate again.
l  Specification for 2 minutes: less than 250 ml
  Note
1000 ml = 1 litre
If specification is exceeded, this indicates that one or more injectors are defective. Check return flow rate from each injector individually.
B - Checking return flow rate of individual injectors
Special tools and workshop equipment required
  A23-10646
t  Hose clamps for hoses up to 25 mm -3094-
  W00-0079
t  Injection rate comparison meter -V.A.G 1348/2 B-
t  4 lengths of hose (made up in the workshop) to fit return line connections on injectors
Each injector normally has a relatively low return flow rate. If the return flow rate at one injector is relatively high compared to the other injectors, that injector is probably defective.
–  Clean all return line connections (e.g. with commercial cleaning solution etc.) before removing.
–  Dry all components after cleaning.
  W00-0614
–  Clamp off fuel return hose -arrow- using hose clamp up to 25 mm -3094-.
  A23-10647
–  Pull return line connections off injectors; to do so, press tabs -1- and -2- down and at the same time pull release pin upwards -arrow-.
  Note
No dirt must be allowed to get into the disconnected return lines or the open connections on the injectors.
–  Connect hoses onto return line connections of all 4 injectors.
–  Run the 4 hoses into injection rate comparison meter -V.A.G 1348/2 B-.
–  Start engine and let it idle for several minutes.
  Caution
Risk of damage to injectors when return lines are disconnected.
Do NOT press the accelerator during this test; the engine must only run at idling speed.
–  When the engine is warm and running at idling speed, the return flow rates at each of the 4 return lines must not differ by more than a small amount.
–  If one injector has a significantly higher return flow rate than the others it must be renewed → Chapter.
Installing fuel return lines
–  Push return line connections carefully onto injectors. The catch should engage audibly. Then press release pin down carefully.
–  Check fuel system for leaks → Chapter.
  A23-10455

Checking return flow rate of injectors at starter cranking speed > < Performing adaption of injector delivery calibration values