Circuit/System Testing

Fuel Injector Balance Test with Active Fuel Injector Tester

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.
1. Verify the battery is fully charged and all accessories are OFF.
2. Ignition OFF, all vehicle systems OFF. Install the CH-47976  Active Fuel Injector Tester, refer to the Active Fuel Injector Tester User Guide. It may take up to 2 min for all vehicle systems to power down.
3. Turn ON the Active Fuel Injector Tester and select the vehicle.
4. Ignition ON, perform the Injector Test with the Active Fuel Injector Tester.
   • If the Active Fuel Injector Tester aborts testing due to fuel pressure or fuel leak down 

     Refer to Fuel System Diagnosis (Without FPCM) , or Fuel System Diagnosis (FPCM) .

   • Go to next step: If the Active Fuel Injector Tester does not abort testing 
5. Compare the test results with the appropriate recommended tolerance.
   • If any fuel injector exceeds the recommended tolerance 

     Replace the appropriate Q17 Fuel Injector(s).

   • Go to next step: If all fuel injectors are within the recommended tolerance 
6. All OK.

Fuel Injector Balance Test with Scan Tool

1. Ignition ON.
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 Q17 Fuel Injector.
3. Select the Fuel Injector Balance Test function within the Special Functions of the scan tool menu.
4. Select a Q17 Fuel Injector to be tested.
5. Press Enter to prime the fuel system.
6. Energize the Q17 Fuel Injector by depressing the Pulse Injector button on the scan tool at the previously selected starting pressure.
7. After the Q17 Fuel Injector stops pulsing, select Min from the Display Mode on the CH 48027  Digital Pressure Gauge and 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  Digital Pressure Gauge.
9. Select Normal from the Display Mode on the CH 48027  Digital Pressure Gauge.
10. Press Enter on the scan tool to bring you back to the Select Injector screen.
11. Repeat steps 3 through 9 for each Q17 Fuel Injector.
12. Subtract the minimum recorded pressure from the starting pressure of each Q17 Fuel Injector. Record the value as the pressure drop for each fuel injector.
13. Obtain a pressure drop value for each Q17 Fuel Injector.
14. Add all of the individual pressure drop values except for the Q17 Fuel Injector suspected of being faulty. This is the total pressure drop.
NOTE:

For engines with 2 banks of cylinders, only measure average pressure drop on cylinders that are on the same bank.

16. Divide the total pressure drop by the number of Q17 Fuel Injectors that were added together. This is the average pressure drop.
17. Verify the difference of any individual Q17 Fuel Injector pressure drop is 20 kPa (3 psi) or less than the calculated average pressure drop.
    • If greater than the specified value 

      Replace the appropriate Q17 Fuel Injector(s).

    • Go to next step: If all fuel injectors are within the specified value 
18. All OK.

Fuel Injector Balance Test with Special Tool

1. Install a CH-48027  Digital Pressure Gauge. Refer to Fuel Pressure Gauge Installation and Removal .
2. Set the amperage supply selector switch on the J-39021  Fuel Injector Coil and Balance Tester to 0.5 - 2.5 amp position.
3. Connect the J-39021  Fuel Injector Coil and Balance Tester to a Q17 Fuel Injector with a J-44602  Injector Test Adapter.
4. Command the Fuel Pump Enable On 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 Q17 Fuel Injector.
5. Command the Fuel Pump Enable On one more time and energize the Q17 Fuel Injector by depressing the Push to Start Test button on the J-39021  Fuel Injector Coil and Balance Tester at the previously selected pressure.
6. After the Q17 Fuel Injector stops pulsing, select Min from the Display Mode on the CH-48027  Digital Pressure Gauge and 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  Digital Pressure Gauge.
8. Select Normal from the Display Mode on the CH-48027  Digital Pressure Gauge.
9. Repeat steps 2 and 4 through 7 for each Q17 Fuel Injector.
10. Subtract the minimum pressure from the starting pressure for each 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 fuel 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.
14. Verify the difference of any individual fuel injector pressure drop is 20 kPa (3 psi) or less than the calculated average pressure drop.
    • If greater than the specified value 

      Replace the appropriate Q17 Fuel Injector(s).