Checking return flow rate of injectors (piezo injectors) at starting speed — VW

🧭 Before you start

Fits: VW Touareg II (7P, 2010–2018)

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• Read rules for cleanliness and the instructions for working on the fuel system .Always follow these rules for cleanliness and instructions before starting work and while working on the fuel system. — Remove engine cover panel .
• Clean all return line connections (e.g. with commercial cleaning solution) before removing.
• All 6 injector units can be connected at the same time or each cylinder can be tested individually.
• This prevents the fuel from being injected during the attempt at starting.
• There is a mechanical fault in the injector unit if the return flow rate is more than three times the lowest measured return flow. This injector unit must be renewed.

🔧 Engine codes this applies to

📋 Procedure

1. ⚠ Read rules for cleanliness and the instructions for working on the fuel system .Always follow these rules for cleanliness and instructions before starting work and while working on the fuel system. — Remove engine cover panel .
2. Clean all return line connections (e.g. with commercial cleaning solution) before removing.
3. Dry all cleaned parts.
4. Pull return line connections off 6 injectors of the two cylinder banks. To do this, push down connection at tabs and pull up centre piece to release (arrow). [Note: Illustration shows cylinder bank 2.On cylinder bank 2 the coolant expansion tank must be detached; coolant hoses remain connected.Adhere strictly to rules of cleanliness. No dirt must be allowed to get into the disconnected fuel return lines or the open connections on the injectors.]
5. Connect return flow meterVAS 6684 as illustrated. [Note: All 6 injector units can be connected at the same time or each cylinder can be tested individually.]

6. Pull electrical connector (1) from fuel pressure regulating valve N276. [Note: This prevents the fuel from being injected during the attempt at starting.]
7. Operate the starter 3 times. (Wait approx. 20 seconds each time after operating starter to prevent it from overheating). [Note: There is a mechanical fault in the injector unit if the return flow rate is more than three times the lowest measured return flow. This injector unit must be renewed.]
8. If necessary, renew injector unit diagnosed as defective .
9. Check O-ring for fuel return connection on injector for damage and deformation.
10. Renew O-ring for fuel return connection.
11. Lubricate O-ring for fuel return connection as well as fuel return connection with assembly oil or clean engine oil.
12. Roll new O-ring with very great care onto fuel return connection. Check that it is correctly seated.
13. Carefully press connections of return lines onto injector. The catch should engage audibly. Then press release pin down carefully.
14. Re-attach electrical connector of fuel pressure regulating valve N276.
15. Delete event memory entry .
16. Checking fuel system for leaks .

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