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Home >> Pontiac >> 2003 >> Sunfire Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - System & Component Tests - 2.2L >> Fuel Systems (CNG) >> Fuel Injector Balance Test Using Tech 2 >> Diagnostic Procedure
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Diagnostic Procedure

  1. Did you perform the Diagnostic System Check - Engine Controls (Alternative Fuels). If yes, go to next step. If no, go to DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS (ALTERNATIVE FUELS) under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 2.2L CAVALIER - BI-FUEL - CNG/GASOLINE article.
  2. Did you perform the Fuel Injector Coil Test? If yes, go to next step. If no, go to FUEL INJECTOR COIL TEST .
  3. Start and idle the engine. Observe the fuel rail pressure sensor parameter using a scan tool. Is the fuel pressure 40-50 psi (276-345 kPa)? If yes, go to next step. If no, go to FUEL SYSTEM DIAGNOSIS (CNG) under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 2.2L ALERO, CAVALIER, GRAND AM & SUNFIRE article.
  4. Turn ignition switch to OFF position. Turn ignition switch to RUN position, engine OFF. Monitor the fuel rail pressure sensor parameter using a scan tool. Does the fuel rail pressure remain constant? If yes, go to next step. If no, go to FUEL SYSTEM DIAGNOSIS (CNG) under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 2.2L ALERO, CAVALIER, GRAND AM & SUNFIRE article.
  5. Using a scan tool, select the FUEL INJECTOR BALANCE TEST function, within the SPECIAL FUNCTIONS menu. Select an injector to be tested. Press ENTER. This will prime the fuel system. Record the fuel pressure indicated by the fuel pressure sensor after the fuel rail pressure stabilizes. This is the first pressure reading. 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. Energize the fuel injector by depressing the PULSE INJECTOR button on the scan tool. This will energize the injector and decrease the fuel pressure. Record the fuel pressure indicated by the fuel rail pressure sensor after the fuel injector has stopped pulsing. This is the second pressure reading. Press ENTER again to bring you back to the SELECT INJECTOR screen.

    Repeat procedure for each fuel injector. Subtract the 2nd pressure reading from the 1st pressure reading for one fuel injector. The result is the pressure drop value. Obtain a pressure drop value for each fuel injector. Add all of the individual pressure drop values. This is the total pressure drop. 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 either higher than the average pressure drop or lower than the average pressure drop by 2.0 psi (14 kPa)? If yes, go to next step. If no, go to SYMPTOMS in TROUBLE SHOOTING - NO CODES - 2.2L CAVALIER - BI-FUEL - CNG/GASOLINE article.

  6. Replace the affected fuel injector. After repair, go to next step.
  7. Operate the vehicle to verify the repair. Does a driveability condition still exist? If yes, go to SYMPTOMS in TROUBLE SHOOTING - NO CODES - 2.2L CAVALIER - BI-FUEL - CNG/GASOLINE article. If no, system is okay at this time.
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