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Removing and Installing Fuel Injectors

The fuel injectors must be removed for inspection or testing. As described above, the injectors are held in the inserts by thick rubber O-rings. To remove the injectors simply pull them straight out, forcing them out of the O-rings, as indicated in Fig. 4-28. Leave the fuel lines attached. Pull straight and pull only on the injectors themselves, not on the fuel lines.

Fig. 4-28. Remove CIS, CIS-E, and CIS-E Motronic fuel injectors by pulling straight out (arrow). Pull on injector body only, not on fuel line.


Some force is required to remove the injectors, and an inexpensive special tool is available which makes the job easier. It fits under the injector fitting and uses a screwdriver for leverage, prying the tool and the injector straight out. One such tool is Volkswagen special tool no. US 1123/4 (order no. TU1 123 004 25 SCP).

It is not normally necessary to remove the injector inserts, except to replace the O-rings and cure air leaks which can cause rough idling. The inserts have an internal hex-shaped socket and are removed using a hex wrench-12 mm or 13 mm depending on the application. The sealing O-rings should be replaced whenever the inserts are removed. See Fig. 4-27 above. Moisten the O-rings with fuel before installing. Clean the threads of the upper insert and install using Loctite® T primer and Loctite® 620 thread locking compound, or equivalent. Torque the upper injector insert to 20 Nm (15 ft. lb.).

Injector installation is the reverse of removal. The thick rubber O-rings should always be replaced. Soak the new ones in fuel for several minutes before installing them. Then press the injector into the insert until the O-ring is fully seated in its groove.

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