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Fuel Injector Balance Test




Fuel Injector Balance Test

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 provide an overview of each diagnostic category.

Circuit/System Description

When performing the fuel injector balance test with the fuel injector tester or the scan tool, the scan tool is first used to enable the fuel pump. The fuel injector tester or the scan tool is then used to pulse each injector for a precise amount of time, allowing a measured amount of fuel to be injected. This causes a drop in the system fuel pressure that can be recorded and used to compare each injector.

Diagnostic Aids

* Monitoring the Current Misfire 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.

Reference Information

Schematic Reference

Engine Controls Schematics (LE9) [1][2]Electrical Diagrams

Connector End View Reference

Component Connector End Views Sunshade - Left (DH6)

Electrical Information Reference

* Circuit Testing Circuit Testing

* Connector Repairs Connector Repairs

* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections

* Wiring Repairs Wiring Repairs

Scan Tool Reference

Control Module References Control Module References for scan tool information

Special Tools

* CH 48027 - Digital Pressure Gauge

* J 39021 - Fuel Injector Coil and Balance Tester

* J 44602 - Injector Test Adapter

* For equivalent regional tools, refer to Special Tools (Diagnostic Tools) Tools and Equipment.

Note:

* DO NOT perform this test if the engine coolant temperature (ECT) is above 94°C (201°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.

* Before proceeding with this test review the User Manual CH 48027-5 for Safety Information and Instructions.

Fuel Injector Balance Test with Special Tool

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

2. Set the amperage supply selector switch on the fuel injector tester to the Balance Test 0.5-2.5 A position.

3. Connect the J 39021 - Fuel Injector Coil and Balance Testerto a Q17 fuel injector using the J 44602 - Adapter.

4. Command the Fuel Pump Enable ON and then OFF three times with a scan tool. On the last command, as the fuel pressure begins to slowly degrade and stabilize, select a fuel pressure within 34 kPa (5 psi) of the maximum pump pressure. Record this fuel pressure. This is the starting pressure at which you will pulse each injector.

5. Command the Fuel Pump Enable ON one more time and energize the fuel injector by depressing the Push to Start Test button on the J 39021 - Fuel Injector Coil and Balance Testerat the previously selected pressure.

6. After the injector stops pulsing, select Min from the Display Mode on the CH 48027 - Gaugeand record the Min pressure.

Note:
New test results will not be recorded if the Min/Max results are not cleared after each injector is tested.

7. Clear the Min/Max results on the CH 48027 - Gauge.

8. Select Normal from the Display Mode on the CH 48027 - Gauge.

9. Repeat steps 3 and 5 through 8 for each Q17 fuel injector.

10. Subtract the minimum pressure from the starting pressure for one fuel injector. The result is the pressure drop value.

11. Obtain a pressure drop value for each Q17 fuel injector.

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

13. Divide the total pressure drop by the number of fuel injectors that were added together. This is the average pressure drop. The difference between any individual pressure drop and the average pressure drop should not be more than 20 kPa (3 psi).

• If the difference between any individual pressure drop and the average pressure drop is more than 20 kPa (3 psi), replace the Q17 fuel injector.

Fuel Injector Balance Test with Scan Tool

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

2. Command the Fuel Pump Enable ON and then OFF three times with a scan tool. On the last command, as the fuel pressure begins to slowly degrade and stabilize, select a fuel pressure within 34 kPa (5 psi) of the maximum pump pressure. Record this fuel pressure. This is the starting pressure at which you will pulse each injector.

3. With a scan tool, select the Fuel Injector Balance Test function within the Special Functions menu.

4. Select an injector to be tested.

5. Press Enter to prime the fuel system.

6. Energize the fuel injector by depressing the Pulse Injector button on the scan tool at the previously selected pressure.

7. After the injector stops pulsing, select Min from the Display Mode on the CH 48027 - Gaugeand record the Min pressure.

Note:
New test results will not be recorded if the Min/Max results are not cleared after each injector is tested.

8. Clear the Min/Max results on the CH 48027 - Gauge.

9. Select Normal from the Display Mode on the CH 48027 - Gauge.

10. Press Enter on the scan tool to bring you back to the Select Injector screen.

11. Repeat steps 4 through 10 for each Q17 fuel injector.

12. Subtract the minimum pressure from the starting pressure for one fuel injector. The result is the pressure drop value.

13. Obtain a pressure drop value for each Q17 fuel injector.

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

15. Divide the total pressure drop by the number of fuel injectors that were added together. This is the average pressure drop. The difference between any individual pressure drop and the average pressure drop should not be more than 20 kPa (3 psi).

• If the difference between any individual pressure drop and the average pressure drop is more than 20 kPa (3 psi), replace the Q17 fuel injector.

Repair Instructions

Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.
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