Fuel Injector Coil Test

Verify the resistance of each fuel injector with one of the following methods:

• If the engine coolant temperature (ECT) sensor is between 10-32°C (50-90°F), the resistance of each fuel injector should be 11-14 ohms.
  • If the injectors measure OK, perform the Fuel Injector Balance Test - Fuel Pressure Test.
  • If not within the specified range, replace the fuel injector.
• If the ECT sensor is not between 10-32°C (50-90°F), measure and record the resistance of each fuel injector with a DMM. Subtract the lowest resistance value from the highest resistance value. The difference between the lowest value and the highest value should be equal to or less than 3 ohms.
  • If the difference is equal to or less than 3 ohms, refer to Fuel Injector Balance Test - Fuel Pressure Test for further diagnosis of the fuel injectors.
  • If the difference is more than 3 ohms, add all of the fuel injector resistance values to obtain a total resistance value. Divide the total resistance value by the number of fuel injectors to obtain an average resistance value. Subtract the lowest individual fuel injector resistance value from the average resistance value. Compute the difference between the highest individual fuel injector resistance value and the average resistance value. Replace the fuel injector that displays the greatest difference above or below the average.

Fuel Injector Balance Test-Fuel Pressure Test

1. Install a CH-48027  . Refer to Fuel Pressure Gauge Installation and Removal .
2. Turn ON the ignition, with the engine OFF.
IMPORTANT:
• The fuel pump relay may need to be commanded ON a few times in order to obtain the highest possible fuel pressure.
• DO NOT start the engine.
3. Command the fuel pump relay ON with a scan tool.
4. Observe the fuel pressure gauge with the fuel pump commanded ON. The fuel pressure should be 345-414 kPa (50-60 psi).
   • If the fuel pressure is not 345-414 kPa (50-60 psi), refer to Fuel System Diagnosis (Without FPCM)  or Fuel System Diagnosis (FPCM) .
5. Monitor the CH-48027  for one minute. The fuel pressure should not decrease more than 34 kPa (5 psi).
   • If the fuel pressure decreases more than 34 kPa (5 psi), refer to Fuel System Diagnosis (Without FPCM)  or Fuel System Diagnosis (FPCM) .
6. Perform the Fuel Injector Balance Test with Special Tool or the Fuel Injector Balance Test with Scan Tool.

Fuel Injector Balance Test with Special Tool

1. Install a CH-48027  . Refer to Fuel Pressure Gauge Installation and Removal .
2. Set the amperage supply selector switch on the fuel injector tester to the Balance Test 0.5-2.5 amp position.
3. Connect the J 39021  to a fuel injector with a J 44602  .
4. Command the fuel pump relay 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 relay ON one more time and energize the fuel injector by depressing the Push to Start Test button on the J 39021  at the previously selected pressure.
6. After the injector stops pulsing, select Min from the Display Mode on the CH-48027  and record the Min pressure.
IMPORTANT: 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  .
8. Select Normal from the Display Mode on the CH-48027  .
9. Repeat steps 2 and 4 through 7 for each fuel injector.
10. Perform the Pressure Drop Calculation.

Fuel Injector Balance Test with Scan Tool

1. Command the fuel pump relay 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.
2. With a scan tool, select the Fuel Injector Balance Test function within the Special Functions menu.
3. Select an injector to be tested.
4. Press Enter to prime the fuel system.
5. Energize the fuel injector by depressing the Pulse Injector button on the scan tool at the previously selected pressure.
6. After the injector stops pulsing, select Min from the Display Mode on the CH-48027  and record the Min pressure.
IMPORTANT: 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  .
8. Select Normal from the Display Mode on the CH-48027  .
9. Press Enter on the scan tool to bring you back to the Select Injector screen.
10. Repeat steps 3 through 9 for each fuel injector.
11. Perform the Pressure Drop Calculation.

Pressure Drop Calculation

1. Subtract the minimum pressure from the starting pressure for one fuel injector. The result is the pressure drop value.
2. Obtain a pressure drop value for each fuel injector.
3. Add all of the individual pressure drop values except for the injector suspected of being faulty. This is the total pressure drop.
4. 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 fuel injector, E-85 only. All other engine, refer to Fuel Injector Cleaning .