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Vehicle Conversion and Installation Flashcards

7 cards from real CNG practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

Read the first 7 Vehicle Conversion and Installation flashcards as text

  1. What minimum bend radius is generally required for rigid stainless steel CNG fuel tubing to prevent cracking?

    Answer: 3 times the outside diameter of the tubing

    A minimum bend radius of 3x the outside diameter prevents work-hardening and cracking in stainless steel CNG tubing.

  2. After completing a CNG conversion, which test should be performed FIRST before any operational test?

    Answer: Static leak test at full operating pressure using approved leak detection solution

    A static leak test confirms all connections are sealed before the system is operated, preventing dangerous fuel releases.

  3. Which document must a CNG conversion installer provide to the vehicle owner upon completion of the installation?

    Answer: Installer certification label and all applicable cylinder certification documents

    The installer must affix a certification label and provide cylinder documentation including manufacturing date, service life, and pressure rating.

  4. CNG cylinders installed in a vehicle's trunk or enclosed cargo area require what safety provision?

    Answer: A pressure relief device vented to the outside of the vehicle

    PRDs in enclosed spaces must vent to the exterior to prevent accumulation of natural gas inside the vehicle if they activate.

  5. Which vehicle system component is most likely to require recalibration after a dedicated CNG conversion to maintain proper air-fuel ratio?

    Answer: Engine Control Module (ECM)

    The ECM must be recalibrated with CNG-specific fuel maps because CNG has different stoichiometry and energy content compared to gasoline.

  6. When routing a CNG fuel line through the vehicle's firewall, the penetration must be:

    Answer: Sealed with a grommet or fitting rated for the pressure and the fuel

    All firewall penetrations must be sealed with a properly rated grommet or bulkhead fitting to prevent gas migration and chafing of the tubing.

  7. What CNG component is specifically designed to prevent gas flow if the fuel line is severed in a collision?

    Answer: Excess Flow Valve (EFV)

    An Excess Flow Valve automatically closes when gas flow exceeds a preset rate, such as what occurs when a fuel line ruptures.