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Home >> Buick >> 2004 >> Century Base >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls 3.1L (Troubleshooting & Diagnosis) >> Engine Controls >> Fuel Injector Balance Test with Special Tool >> Test Description

Test Description

The numbers below refer to the step numbers 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. 6:  If the pressure drop value for each fuel injector is within 20 kPa (3 psi) of the average pressure drop value, the fuel injectors are flowing properly.
Fuel Injector Balance Test Procedure

Step Action Values Yes No
1 Did you perform the Diagnostic System Check-Engine Controls? - Go to Step 2  Go to Diagnostic System Check - Engine Controls
2 Did you perform the Fuel Injector Coil Test? - Go to Step 3  Go to Fuel Injector Coil Test 
3 
IMPORTANT: Do not perform this test if the ECT is above 94°C (201°F).
Observe the ECT parameter with a scan tool.Does the scan tool indicate that the ECT parameter is less than the specified value?		 94°C (201°F) Go to Step 4  -
4
IMPORTANT: Verify adequate fuel in the fuel tank before proceeding with this diagnostic.
  1. Turn OFF the ignition.
  2. Install the J 34730-1A  Fuel Pressure Gage and the fuel pressure gage fitting. Refer to Fuel Pressure Gage Installation and Removal .
  3. Turn ON the ignition, with the engine OFF.
  4. Command the fuel pump relay ON with a scan tool.
    5. IMPORTANT:
    • You may need to command the fuel pump relay ON a few times, in order to obtain the highest possible fuel pressure.
    • Do not start the engine.
  5. Observe the J 34730-1A  , with the fuel pump relay commanded ON.
Is the fuel pressure within the specified range?		 358-407 kPa (52-59 psi) Go to Step 5  Go to Fuel System Diagnosis 
5
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.
Observe the J 34730-1A  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 6 
6 
  1. Connect the J 39021  Fuel Injector Coil/Balancer Tester, J 39021-210 Injector Selector Switch Box, and J 39021-410  Fuel Injector Harness Adapter to the fuel injector multi-way connector.
  2. Set the amperage supply selector switch on the fuel injector tester to the balance test 0.5-2.5 amp position.
  3. Command the fuel pump relay ON and then OFF with a scan tool.
  4. Record the fuel pressure indicated by the J 34730-1A  after the fuel pressure stabilizes. This is the first 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 Push to Start test button on the fuel injector tester.
  6. Record the fuel pressure indicated by the J 34730-1A  . This is the second fuel pressure reading.
  7. Repeat steps 1 through 6 for each fuel injector.
  8. Subtract the second pressure reading from the first pressure reading for one fuel injector. The result is the pressure drop value.
  9. Obtain a pressure drop value for each fuel injector.
  10. Add all of the individual pressure drop values. This is the total pressure drop.
  11. 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 more than the average pressure drop or less than the average pressure drop by the specified value?		 20 kPa (3 psi) Go to Step 7  Go to Symptoms - Engine Controls 
7 Clean the fuel injector. Refer to Fuel Injector Cleaning Procedure .
Did you complete the action?		 - Go to Step 8  -
8 Operate the vehicle in order to verify the repair.
Does a driveability condition still exist?		 - Go to Symptoms - Engine Controls  System OK
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