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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 244 (ENGINE CONTROLS - SYSTEM & COMPONENT TESTING - 6.0L W/BiFuel & CNG) >> Fuel Systems >> Fuel Injector Balance Test With Special Tool >> Diagnostic Procedures

Diagnostic Procedures

WARNING: This page is about a different car, the 2003 GMC Sierra, 2003 GMC Savana, 2003 Chevrolet Silverado, and 2003 Chevrolet Chevy Express. However, it is still accessible from the selected car via links, so may be relevant.
  1. Perform Diagnostic System Check Alternative Fuels - Engine Controls. See DIAGNOSTIC SYSTEM CHECK - ALTERNATIVE FUELS under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 6.0L CHEVY EXPRESS & SAVANA - BI-FUEL & CNG or DIAGNOSTIC SYSTEM CHECK - ALTERNATIVE FUELS under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 6.0L SILVERADO & SIERRA - BI-FUEL & CNG article. After performing Diagnostic System Check - Engine Controls, go to next step.
  2. Perform FUEL INJECTOR COIL TEST  . After performing Fuel Injector Coil Test, go to next step.
  3. Start and operate engine at idle. Observe the fuel rail pressure sensor parameter with a scan tool. Is the fuel pressure within 160-170 psi (1103-1172 kPa)? If yes, go to next step. If no, diagnose fuel system. Refer to FUEL SYSTEM DIAGNOSIS under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 6.0L CHEVY EXPRESS, SAVANA, SIERRA & SILVERADO - BI-FUEL/CNG article.
  4. Turn ignition off. Turn ignition on, with engine off. Monitor the fuel rail pressure sensor parameter with a scan tool. Does the fuel rail pressure remain constant? If yes, go to next step. If no, diagnose fuel system. Refer to FUEL SYSTEM DIAGNOSIS under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 6.0L CHEVY EXPRESS, SAVANA, SIERRA & SILVERADO - BI-FUEL/CNG article.
    5. NOTE: DO NOT repeat any portion of this test without starting the engine in order to prevent engine from flooding.
  5. Turn ignition off. Connect the Fuel Injector Tester (J-39021) to a fuel injector. Set the amperage supply selector switch on the fuel injector tester to the Balance Test 0.5-2.5 amp position. Turn ignition on, with engine off. Record fuel pressure indicated by the fuel rail pressure sensor after fuel pressure stabilizes. This is the first pressure reading. Record fuel pressure value immediately after the CNG fuel injector stops pulsing. The fuel pressure may rise after fuel injector stops pulsing. DO NOT record the higher fuel pressure value. Energize the CNG fuel injector by depressing the Push to Start Test button on the fuel injector tester. Record fuel pressure indicated by the fuel rail pressure sensor. This is the second fuel pressure reading. Repeat procedure for each fuel injector. Subtract the second pressure reading from the first 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 more than the average pressure drop or less than the average pressure drop by 2.0 psi (14 kPa)? If yes, go to next step. If no, refer to FUEL SYSTEM DIAGNOSIS under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 6.0L CHEVY EXPRESS, SAVANA, SIERRA & SILVERADO - BI-FUEL/CNG article.
  6. Replace the affected CNG fuel injector. After replacing injector(s), go to next step.
  7. Operate system in order to verify repair. Did you correct the condition? If yes, system is okay. If no, go to SYMPTOMS in TROUBLE SHOOTING - NO CODES - 6.0L CHEVY EXPRESS, SAVANA, SIERRA & SILVERADO - BI-FUEL & CNG article.
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