Checking injectors for leaks and quantity injected: VW Golf IV / Bora (AQN, AQP, AUE, AXQ, …)

🧭 Before you start

Remove the intake manifold and lift the fuel rail out with its lines connected. Pull fuse 28 and run the fuel pump with the remote control to watch each injector for drips. For the quantity check, connect the 121-pin adapter, bridge the pump sockets, and fire each injector into its own measuring glass for 30 seconds. Compare the volumes on a level surface, renew any injector that leaks or delivers out of line, then refit the rail and manifold.

Fits: VW Golf IV / Bora (1J)

• Renewed: measuring beakers, defective injector

Don't miss

• Leave the fuel lines attached to the rail; it comes out as one unit.
• More than 1 to 2 drops per minute from any injector means it gets renewed.
• On BFH the injector connector catch has to be pressed in the arrow direction before it releases.
• Run every injector for the same 30 seconds and use fresh beakers each time.
• Read the volumes with the beakers standing level, side by side.
• Petrol is spraying in the open here, so keep ignition sources well away; general practice.

Written for this job from the workshop steps below · TorqFix editorial.

🔧 Engine codes this applies to

📐 47 workshop diagrams for AQN

Real factory drawings for this job — timing marks, bolt locations and routing. Locked in the free view.

📋 Procedure

1. Remove intake manifold .
2. Now remove complete fuel rail (fuel lines remain connected) .
3. Remove fuse holder cover.
4. Pull fuse No. 28 out of fuse holder.
5. Connect remote control for V.A.G 1348V.A.G 1348/3A with adapter cableV.A.G 1348/3-2 to contact 28a of fuel pump and battery positive (+).

6. Operate remote control.
7. Check injectors for leaks (visual check). No more than 1 to 2 drops per minute must escape from each valve when fuel pump is running.
8. Switch off ignition.
9. Replace defective injector with new one for engine codes AQP, AUE and BDE , or for engine codes BFH, BJS and BML
10. Connect 121-pin adapter cableV.A.G 1598/31 to control unit wiring harness. The engine control unit remains disconnected.
11. Detach injector connectors.
12. For engine code BFH you must press connector catch in direction of arrow.
13. Switch on ignition.
14. Bypass sockets 2+65 of 121-pin adapter cableV.A.G 1598/31 with test cables from auxiliary measuring setV.A.G 1594C. Fuel pump must start up. [Note: This step serves only to have the fuel pump running when the engine is stopped.]
15. Insert injector to be checked into measuring glass from injection rate testerV.A.G 1602.
16. Connect a contact of injector to be tested to engine earth using auxiliary cables from auxiliary measuring setV.A.G 1594C.
17. Connect second injector contact with auxiliary cable to remote control for V.A.G 1348V.A.G 1348/3A using adapter cableV.A.G 1348/3-2.
18. Connect crocodile clip to battery (+).
19. Operate remote control for V.A.G 1348V.A.G 1348/3A for 30 seconds.
20. Repeat check on other injectors. Use new measuring beakers.
21. After all injectors have been activated, place measuring beakers on level surface and compare volume injected. Specification for:
22. Switch off ignition.
23. Renew defective injector.

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