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Home >> Cadillac >> 2002 >> Escalade EXT >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - System & Component Testing >> Fuel System (Bi-Fuel & CNG) >> Fuel Injector Balance Test With Special Tool >> Diagnostic Procedure

Diagnostic Procedure

  1. Perform Alternative Fuels Diagnostic System Check - Engine Controls. See ALTERNATIVE FUELS DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS under SELF-DIAGNOSTIC SYSTEM in appropriate SELF-DIAGNOSTICS article. After performing Alternative Fuels Diagnostic System Check - Engine Controls, go to next step.
  2. Did you perform Fuel Injector Coil Test? If yes, go to next step. If no, go to FUEL INJECTOR COIL TEST (BI-FUEL & CNG) .
  3. Start and idle engine. Observe Fuel Rail Pressure (FRP) sensor parameter with scan tool. Is fuel pressure within 40-50 psi (275-345 kPa)? If yes, go to next step. If no, go to FUEL SYSTEM DIAGNOSIS (BI-FUEL & CNG) .
  4. Turn OFF the ignition. Turn ON the ignition, with the engine OFF. Monitor Fuel Rail Pressure (FRP) sensor parameter with scan tool. Does fuel rail pressure remain constant? If yes, go to next step. If no, go to FUEL SYSTEM DIAGNOSIS (BI-FUEL & CNG) .
    5. CAUTION: DO NOT repeat any portion of this test before running engine in order to prevent engine from flooding.
    NOTE: Record fuel pressure value immediately after CNG fuel injector stops pulsing. Fuel pressure may rise after fuel injector stops pulsing. DO NOT record higher fuel pressure value.
  5. Turn OFF the ignition. Connect Fuel Injector Tester (J 39021) to a fuel injector. Set amperage supply selector switch on fuel injector tester to Balance Test.5-2.5-amp position. Turn ON the ignition, with the engine OFF. Record fuel pressure indicated by FRP sensor after fuel pressure stabilizes. This is first pressure reading.

    Energize CNG fuel injector by depressing "Push To Start Test" button on fuel injector tester. Record fuel pressure indicated by FRP sensor. This is second fuel pressure reading. Repeat for each fuel injector. Subtract second pressure reading from first pressure reading for one fuel injector. The result is pressure drop value. Obtain a pressure drop value for each fuel injector. Add all individual pressure drop values. This is total pressure drop. Divide total pressure drop by number of fuel injectors. This is average pressure drop. Does any fuel injector have a pressure drop value that is more than average pressure drop or less than average pressure drop by 2.0 psi (14 kPa)? If yes, go to next step. If no, go to SYMPTOM DIAGNOSIS under SYMPTOMS (BI-FUEL & CNG) in TROUBLE SHOOTING - NO CODES - TRUCKS article.

  6. Replace affected CNG fuel injector. After repairs, go to next step.
  7. Operate vehicle in order to verify repair. Does a driveability condition still exist? If yes, go to SYMPTOM DIAGNOSIS under SYMPTOMS (BI-FUEL & CNG) in TROUBLE SHOOTING - NO CODES - TRUCKS article. If no, system is okay.
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