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Fuel Injector Balance Test

Fuel Injector Balance Test

Diagnostic Instructions


• Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

• Review Strategy Based Diagnosis for an overview of the diagnostic approach.

• Diagnostic Procedure Instructions provides an overview of each diagnostic category.


Circuit/System Description

The fuel injector balance test is performed while the engine is running at idle. The scan tool pressurizes the fuel rail to a predetermined pressure before each injector is pulsed for a precise amount of time allowing a measured amount of the fuel to be injected. This causes a drop in the system fuel pressure that is recorded and used to compare each injector.

Diagnostic Aids


• Monitoring the Current Misfire Counters may help to isolate the fuel injector that is causing the condition.

• Operating the vehicle over a wide temperature range may help isolate the fuel injector that is causing the condition.


Component Testing

Note
• DO NOT perform this test if the engine coolant temperature (ECT) is above 60°C (140°F). Irregular fuel pressure readings may result due to hot soak fuel boiling.

• Verify that adequate fuel is in the fuel tank and that the battery is fully charged before proceeding with this diagnostic. It may be necessary to install a battery charger.



Fuel Injector Balance Test

1. Verify the correct low side fuel pressure. Refer to Fuel System Diagnosis .

2.
Note

The engine speed must be between 600-1000 RPM to perform this test.


Engine running at normal operating temperature. With a scan tool, select the Fuel Injector Balance function within the Output Controls menu.

3. Select and test an injector. Repeat for each injector in order to obtain a pressure drop value for each injector.

4. After all injectors are tested, record the fuel pressure drops.

5. Add all of the individual pressure drop values except for the injector suspected of being faulty. This is the total pressure drop.

6. Divide the total pressure drop by the number of fuel injectors that were added together. This is the average pressure drop.

7. Multiply the average pressure drop by 0.20. This is the acceptable variance from the average pressure drop, 20 percent.

8. If the difference between any individual pressure drop and the average pressure drop is more than the acceptable variance, replace the fuel injector.


Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Direct Fuel Injector Replacement