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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
  WARNING
t  Always read rules for cleanliness and instructions for working on fuel system → Chapter.
t  Follow these instructions and rules for cleanliness before starting work and while working on the fuel system.
–  Remove engine cover panel → Chapter.
   
–  Disconnect hose connection downstream of pressure retention valve -arrow- at banjo bolt connection.
  A23-10145
–  Seal off the open return connection with a plug -1-.
–  Hold end of this hose -3- (lengthen with hose -4- if necessary) in a suitable container to measure 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
t  Injection rate comparison meter -V.A.G 1348/2 B-
t  6 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 (with commercial cleaning solution or similar) before removing.
–  Dry all components after cleaning.
  A23-10327
–  Clamp off fuel return line downstream of pressure retention valve using hose clamp up to 25 mm -3094-.
  A23-10317
–  Pull return line connections off injectors; to do so, press both tabs down and at the same time pull centre piece up to release connection -arrow-.
  Note
t  Illustration shows cylinder bank 2.
t  On cylinder bank 2 the coolant expansion tank must be detached; coolant hoses remain connected.
t  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 6 injectors.
–  Run the 6 hoses into injection rate comparison meter -V.A.G 1348/2 B-.
–  Start engine and let it idle for several minutes.
  Caution
Do NOT press the accelerator during this test; the engine must only run at idling speed.
Running the engine at higher speeds with the return lines disconnected will cause damage to the injectors.
–  When the engine is warm and running at idling speed, the return flow rates at each of the 6 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
–  Renew O-rings at all return line connections.
  Note
Lubricate all O-rings with engine oil or assembly oil before installing.
–  Push the return line connections carefully over the new seals and onto the injectors. The catch should engage audibly. Then press release pin down carefully.
–  Push the return line connections carefully over the new seals and onto the injectors. The catch should engage audibly. Then press release pin down carefully.
–  Check fuel system for leaks → Chapter.
  A23-10032

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