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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 1851 (Engine Controls And Fuel - 3.5L (L66) - Troubleshooting & Diagnosis) >> Fuel Injector Balance Test with Special Tool >> Test Description

Test Description

WARNING: This page is about a different car, the 2007 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.

The numbers below refer to the step numbers on the diagnostic table.

  1. 3:  The engine coolant temperature must be less than the operating temperature in order to avoid irregular fuel pressure readings due to hot soak fuel boiling.
  2. 4:  The engine coolant temperature must be less than the operating temperature in order to avoid irregular fuel pressure readings due to hot soak fuel boiling.
  3. 5:  This step checks that the fuel pressure is within the specified operating range.
  4. 6:  This step checks for a steady fuel pressure reading. A steady fuel pressure reading indicates that the fuel system is operating properly.
  5. 7:  The fuel injectors are flowing properly if the pressure drop value for each fuel injector is within 10 kPa (1.5 psi) of the average pressure drop value. Calculate the pressure drop value for each fuel injector by subtracting the second pressure reading from the first pressure reading. Refer to the examples in the preceding table.
Fuel Injector Balance Test with Special Tool

Step Action Value(s) Yes No
1 Did you perform the Diagnostic System Check - Vehicle? - Go to Step 2  Go to Diagnostic System Check - Vehicle
2 Was the Fuel Injector Coil Test performed? - Go to Step 3  Go to Fuel Injector Solenoid Coil Test 
3 
IMPORTANT: DO NOT perform this test if the engine coolant temperature (ECT) is above 94°C (201°F).
Is the ECT more than the specified value?		 94°C (201°F) Go to Step 4  Go to Step 5 
4 
IMPORTANT: Verify that adequate fuel is in the fuel tank before proceeding with this diagnostic.
Allow the engine to cool to less than the specified value.Is the engine coolant temperature less than the specified value?		 94°C (201°F) Go to Step 5  -
5 
CAUTION: Refer to Fuel Gage Leak Caution .
IMPORTANT: The fuel pressure may vary slightly when the fuel pump stops operating. After the fuel pump stops operating, the fuel pressure should stabilize and remain constant.
  1. Install the SA9127E  Fuel Pressure Gage. Refer to Fuel Pressure Gage Installation and Removal .
    2. 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.
  2. Command the fuel pump relay ON with the scan tool or cycle the ignition switch ON and then OFF. Refer to Scan Tool Output Controls .
  3. Observe the reading on the fuel pressure gage.
Is the fuel pressure within the specified range?		 330-382 kPa (48-56 psi) Go to Step 6  Go to Fuel System Diagnosis 
6  Turn OFF the fuel pump.
Does the fuel pressure reading remain constant?		 - Go to Step 7  Go to Fuel System Diagnosis 
7 
  1. Disconnect the fuel injector electrical connectors.
  2. Connect the J 39021  Fuel Injector Tester power leads to B+ and ground. See Special Tools .
  3. Set the amperage supply selector switch on the fuel injector tester to the Balance Test 0.5-2.5 amp position.
  4. Connect the J 39021  to a fuel injector. See Special Tools .
  5. Turn the ignition switch ON and then OFF, in order to energize the fuel pump.
  6. Record the fuel pressure indicated by the fuel pressure gage after the fuel pressure stabilizes. This is the 1st pressure reading.
  7. Energize the fuel injector by depressing the Push to Start Test button on the fuel injector tester.
    8. IMPORTANT: Record the fuel pressure value immediately after the fuel injector stops pulsing. The fuel pressure may rise after the fuel injector stops pulsing. DO NOT record the higher fuel pressure value.
  8. Record the fuel pressure indicated by the fuel pressure gage after the fuel pressure gage needle has stopped moving. This is the 2nd pressure reading.
  9. Repeat Step 4-8 for each fuel injector.
  10. Subtract the 2nd pressure reading from the 1st pressure reading for one fuel injector. The result is the pressure drop value.
  11. Obtain a pressure drop value for each fuel injector.
  12. Add all of the individual pressure drop values. This is the total pressure drop.
  13. Divide the total pressure drop by the number of fuel injectors. This is the average pressure drop.
Does any fuel injector have a pressure drop value that is higher or lower than the average pressure drop by the specified value?		 10 kPa (1.5 psi) Go to Step 8  Go to Symptoms - Engine Controls 
8
NOTE: Do Not repeat any portion of this test before running the engine in order to prevent the engine from flooding.
Re-test any fuel injector that does not meet the specification. Follow the procedures in step 7.Does any fuel injector still have a pressure drop value that is higher or lower than the average pressure drop by the specified value?		 10 kPa (1.5 psi) Go to Step 9  Go to Symptoms - Engine Controls 
9 Replace any faulty fuel injectors. Refer to Fuel Injector Replacement .
Did you complete the replacement?		 - Go to Step 10  -
10
  1. Start the engine.
  2. Perform the idle learn procedure. Refer to Idle Learn .
Does an engine performance concern still exist?		 - Go to Symptoms - Engine Controls  System OK
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