Without VAG
FUEL INJECTOR TESTINGThe first step in any Motronic troubleshooting must be to check the On Board Diagnosis (OBD) fault memory, then find and correct any faults that may be indicated. Refer to COMPUTERIZED ENGINE CONTROLS. for more information.
NOTE: The hall sender signal from the ignition system must be OK and reaching the Motronic control unit for this test to be valid.
CAUTION: Only connect and disconnect test equipment or LED test light with the ignition switch turned OFF. Failure to do so may damage sensitive electronic components in the Motronic control unit.
CHECKING INJECTOR POWER AND GROUND
Fuel Injector Main Harness Connector Terminal I.D.:
- Disconnect the injector main harness connector located near the end of the fuel rail.
- Connect an LED test light between terminals 1 and 5 of the harness connector (B).
- Briefly operate the starter. The test light should flicker, indicating that voltage is reaching the connector and that the control unit is switching the injector ground.
- Repeat above test using LED light at terminals 2 and 5, terminals 3 and 5, and terminals 4 and 5 making sure to turn ignition switch OFF between tests.
If the LED stays ON continuously, there is a faulty ground connection. Check the Motronic control unit ground connection at the intake manifold, and the ground strap between the engine/transmission assembly and the battery.
If the LED does not light at all, the problem may be faulty wiring between the harness connector (B) and the Motronic control unit. If the wiring is OK, then the Motronic control unit may be faulty, refer to COMPUTERIZED ENGINE CONTROLS.
CHECKING INJECTOR RESISTANCE
Fuel Injector Main Harness Connector Terminal I.D.:
- Using a suitable digital multimeter, set to measure resistance (ohms), check resistance between terminals 1 and 5 of the fuel rail mounted connector (A). Fuel injector resistance should be:
15 to 20 ohms
- Repeat resistance check using meter at terminals 2 and 5, terminals 3 and 5, and terminals 4 and 5 making sure to turn ignition switch OFF between tests.
- If any of the injector resistance readings are incorrect, check the wiring between the main connector (A) and the individual injector connector.
- If the wiring between the main connector (A) and injector connector is OK, check resistance between the terminals on the injector itself. If reading is still incorrect the injector is faulty and should be replaced.