Fuel Injector Balance Test
Diagnostic Instructions
Circuit/System Description
The fuel injector balance test is performed while the engine is running at idle. The scan tool pressurises 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 before proceeding with this diagnostic. |
Fuel Injector Balance Test
- Verify the correct low side fuel pressure. Refer to Fuel System Diagnosis .
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.
- Select and test an injector. Repeat for each injector in order to obtain a pressure drop value for each injector.
- After all injectors are tested, record the fuel pressure drops.
- Add all of the individual pressure drop values except for the injector suspected of being faulty. This is the total pressure drop.
- Divide the total pressure drop by the number of fuel injectors that were added together. This is the average pressure drop.
- Multiply the average pressure drop by 0.20. This is the acceptable variance from the average pressure drop, 20 percent.
⇒ | 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.
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Fuel Injection Fuel Rail Assembly Replacement - Bank 1 : LF1, LFW |
• |
Fuel Injection Fuel Rail Assembly Replacement - Bank 2 : LF1, LFW |
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