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Home >> GMC >> 2003 >> Safari Van Cargo, AWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 1558 (Engine Controls And Fuel - 3.5L (L66) - Troubleshooting & Diagnosis) >> Fuel Injector Balance Test with Tech 2 >> System Description >> 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 number below refers to the step number on the diagnostic table.

  1. 3:  The engine coolant temperature (ECT) must be below 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 of this fuel system.
  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 Tech 2

Step Action Values Yes No
1 Did you perform the Diagnostic System Check - Vehicle? - Go to Step 2  Go to Diagnostic System Check - Vehicle
2 Did you perform the Fuel Injector Coil Test? - 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).
Observe the ECT Sensor parameter with a scan tool.Is the ECT Sensor parameter less than the specified value?		 94°C (201°F) Go to Step 5  Go to Step 4 
4  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 
IMPORTANT: Verify that adequate fuel is in the fuel tank before proceeding with this diagnostic.
  1. Turn OFF the ignition.
  2. Turn OFF all accessories.
  3. Install the SA9127E  fuel pressure gage. Refer to Fuel Pressure Gage Installation and Removal .
  4. Turn ON the ignition, with the engine OFF.
    5. 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.
  5. Command the fuel pump relay ON with the scan tool. Refer to Scan Tool Output Controls .
  6. Observe the fuel pressure gage, with the fuel pump operating.
Is the fuel pressure within the specified value?		 330-382 kPa (48-56 psi) Go to Step 6  Go to Fuel System Diagnosis 
6  Monitor the fuel pressure gage for 1 minute.
Does the fuel pressure decrease by more than the specified value?		 34 kPa (5 psi) Go to Fuel System Diagnosis  Go to Step 7 
7 
NOTE: Do Not repeat any portion of this test before running the engine in order to prevent the engine from flooding.
  1. With a scan tool, select the Fuel Injector Balance Test function, within the Special Functions menu.
  2. Select an injector to be tested.
  3. Press Enter. This will prime the fuel system.
  4. Record the fuel pressure indicated by the fuel pressure gage after the fuel pressure stabilizes. This is the 1st pressure reading.
    5. 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.
  5. Energize the fuel injector by depressing the Pulse Injector button on the scan tool. This will energize the injector and decrease the fuel pressure. Refer to Scan Tool Output Controls .
  6. Record the fuel pressure indicated by the fuel pressure gage after the fuel injector has stopped pulsing. This is the 2nd pressure reading.
  7. Press Enter again to bring you back to the Select Injector screen.
  8. Repeat for each fuel injector.
  9. Subtract the 2nd pressure reading from the 1st pressure reading for one fuel injector. The result is the pressure drop value.
  10. Obtain a pressure drop value for each fuel injector.
  11. Add all of the individual pressure drop values. This is the total pressure drop.
  12. Divide the total pressure drop by the number of fuel injectors. This is the average pressure drop.
Is the difference between any individual pressure drop and the average pressure drop more than the specified value?		 10 kPa (1.5 psi) Go to Step 8  Go to Symptoms - Engine Controls 
8 Replace the affected fuel injectors.
Did you complete the replacement?		 - Go to Step 9  -
9
  1. Start the engine.
  2. Perform the idle learn procedure. Refer to Idle Learn .
Does an engine performance concern still exist?		 - System OK Go to Symptoms - Engine Controls 
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