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Checking return flow rate of injectors at starter cranking speed > < Performing adaption of correction values for injectors

A4 Mk3

Checking return flow rate of injectors with engine running
Checking return flow rate of injectors with engine running
Checking return flow rate of all injectors
  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 open return line connection with a clean plug -2-.
–  Hold end of fuel return hose -1- (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.
Checking return flow rate of individual injectors
Special tools and workshop equipment required
  A23-10591
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-.
  A23-10592
–  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
  Note
Lubricate all seals with engine oil or assembly oil before installing.
–  Renew O-rings for all return line connections.
–  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 correction values for injectors