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Testing Fuel Injectors

The Digifant I fuel injectors are basically the same as those used in Digifant II. The difference on Digifant I fuel injectors is that there is one power supply serving all injectors, but a separate ground wire for each injector. The control unit still makes the ground connection to open the injectors, all at the same time. The separate ground wire allows the control unit to monitor the operation of each injector to detect faults.

This heading covers only the electrical tests of Digifant I injectors. For a description of fuel injector operation or for injector removal and installation, see 4.8 Fuel Injectors (Digifant II). For the following tests to be valid, the Hall sender must be operating correctly. See IGNITION for more information.


Volkswagen specifies that the first step in any Digifant I system troubleshooting must be to check the OBD fault memory, and to find and correct any faults that may be indicated.

To test Digifant I injectors:
1. Disconnect the injector harness connector. The connector is located at the fuel-pressure test port end of the fuel rail. See Fig. 8-3.

Fig. 8-3. Digifant I injector wiring harness connector shown disconnected. Numbers indicate connector terminals.

2. Connect an LED test light between terminals 1 and 5 of the harness connector leading to the control unit, then operate the starter. The test light should flicker. Turn off the ignition.
3. Repeat the above test for terminals 2 and 5, 3 and 5, and 4 and 5.
4. Connect a digital ohmmeter to terminals 1 and 5 of the harness connector leading to the injectors. The resistance should be 15 to 20 ohms.
5. Repeat the above test for terminals 2 and 5, 3 and 5, and 4 and 5.

If, in the LED tests, the test light is on continuously, the ground wire between the battery and the control unit may be faulty. Check the connection and replace the wire if necessary. If the test light does not flicker at all, check the wiring between the connector and the control unit and repair any faults. If the wiring is OK, then the control unit is most likely faulty.


If the control unit is replaced, the new one must be reset. See 8.2 Resetting Digifant I Control Unit.

If any of the injector resistance readings are incorrect, disconnect the harness connector for that injector and check the wiring. If the wiring is OK, then the injector is most likely faulty.

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