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HOMESERVICE MANUALSCHEVROLET2008CHEVY EXPRESS G2500, VAN CARGO, 6.6 6REPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 487 (ENGINE CONTROLS - 6.0L - ALTERNATIVE FUELS (TROUBLESHOOTING))TROUBLESHOOTINGBACKFIRE
2008 Chevrolet Chevy Express G2500, Van Cargo, 6.6 6

Section 487 (Engine Controls - 6.0L - Alternative Fuels (Troubleshooting)): Troubleshooting: Backfire

2008 Chevrolet Chevy Express G2500, Van Cargo, 6.6 6SECTION Backfire
WARNING: This page is about a different car, the 2004 GMC Sierra and 2004 Chevrolet Silverado. However, it is still accessible from the selected car via links, so may be relevant.
Backfire

Checks Action
DEFINITION: The fuel ignites in the intake manifold, or in the exhaust system, making a loud popping noise.
Preliminary Checks Refer to Important Preliminary Checks in Symptoms - Engine Controls  .
Ignition System Checks
    IMPORTANT: A higher secondary ignition voltage is required to operate the vehicle on CNG than on gasoline.
  • Inspect for proper secondary ignition system voltage output using only the J 26792  spark tester.
  • Remove and inspect the spark plugs for the following conditions:
    • Wet plugs
    • Cracks
    • Wear
    • Improper gap
    • Burned electrodes
    • Heavy deposits
  • Test for proper ignition system operation.
  • Test for crossfire between spark plugs. Test for spark plug wire failure. Wetting down the secondary ignition system with a water spray bottle may aid in locating damaged or deteriorated components.
Engine Mechanical Checks
  • Inspect the engine for the following:
    • Intake manifold leaks
    • Improper valve timing
    • Proper engine cylinder compression
    • Sticking or leaking intake or exhaust valves
    • Exhaust system leakage
  • Inspect the intake and exhaust system for casting flash.
Fuel System Checks Perform fuel system diagnosis. Refer to Fuel System Diagnosis  .
Additional Checks
  • Review service bulletins for PCM programming updates.
  • Verify that the correct CNG software and calibration has been programmed into the PCM.
  • Test for proper operation of the AFO Enable circuit.
RENDER: 1.0x

NO RELATED

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.