Fuel Injector Balance Test with Special Tool
Fuel Injector Balance Test with Special Tool
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (Diagnostic System Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Strategy Based Diagnosis) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Diagnostic Procedure Instructions) provides an overview of each diagnostic category.
Diagnostic Fault Information
Circuit/System Description
The scan tool is first used to energize the fuel pump relay. The fuel injector tester is then used to pulse each injector for a precise amount of time, allowing a measured amount of fuel into the manifold. This causes a drop in system fuel pressure that can be recorded and used to compare each injector.
Diagnostic Aids
* Monitoring the misfire current counters, or misfire graph, 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.
* Perform the fuel injector balance test within the conditions of the customers concern. A fuel injector condition may only be apparent at a certain temperature, or under certain conditions.
Reference Information
Schematic Reference
Engine Controls Schematics ([1][2]Electrical Diagrams)
Description and Operation
Fuel System Description (Fuel System Description)
Scan Tool Reference
Control Module References (Programming and Relearning) for scan tool information
Special Tools
J 39021 Fuel Injector Coil and Balance Tester
Component Testing
Fuel Injector Balance Test with Special Tool
1. Ignition ON, verify the scan tool engine coolant temperature (ECT) parameter is less than 94°C (201°F).
• If greater than the specified range, allow the engine to cool before proceeding.
2. Ignition OFF, install the fuel pressure gauge. Refer to Fuel Pressure Gauge Installation and Removal (Fuel Pressure Gauge Installation and Removal).
3. Ignition ON, verify the fuel pressure is within 365-414 kPa (53-60 psi).
• If not within the specified range, refer to Fuel System Diagnosis (Fuel System Diagnosis) for further diagnosis of the fuel system.
4. Monitor the fuel pressure gauge for 1 minute. Verify the fuel pressure does not drop greater than 34 kPa (5 psi).
• If greater than the specified range, refer to Fuel System Diagnosis (Fuel System Diagnosis) for further diagnosis of the fuel system.
Caution: Do Not repeat any portion of this test before running the engine in order to prevent the engine from flooding.
Note: DTCs will need to be clear after completing this procedure.
5. Connect the J 39021 to a fuel injector with the amperage supply selector switch on the fuel injector tester to the Balance Test 0.5-2.5 amp position.
6. Command the fuel pump relay ON with a scan tool and record the fuel pressure indicated by the fuel pressure gauge after the fuel pressure stabilizes. This is the first pressure reading.
Note:
* Repeat this step for each fuel injector in order to obtain a pressure drop value for each fuel injector.
* The fuel pressure may rise after the fuel injector stops pulsing. Record the fuel pressure value immediately after the fuel injector stops pulsing. DO NOT record the higher fuel pressure value.
7. Energize the fuel injector by depressing the Push to Start Test button on the fuel injector tester. Record the fuel pressure indicated by the fuel pressure gauge after the fuel injector has stopped pulsing. This is the second pressure reading.
8. Add all of the individual pressure drop values in order to calculate the total pressure drop. Divide the total pressure drop by the number of fuel injectors in order to calculate the average pressure drop. The difference between any individual pressure drop and the average pressure drop should not be greater than 20 kPa (3 psi).
• If the difference between any individual pressure drop and the average pressure drop is greater than the specified range, replace the fuel injector.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
Fuel Injection Fuel Rail Assembly Replacement (Service and Repair)