Practice Test Geeks(CNG) Compressed Natural Gas Practice Test
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Systems 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 Systems flashcards as text

  1. A CNG technician notices the fuel gauge reads empty but the pressure gauge shows 200 psi. What is the most likely explanation?

    Answer: Gas remains but at too low a pressure for practical use

    At 200 psi there is still some CNG in the cylinders, but it is below the pressure needed for reliable engine operation and represents near-empty.

  2. Which CNG system component is responsible for metering the correct amount of gas into the engine's intake?

    Answer: Gas injectors or mixer

    Gas injectors (in sequential systems) or a mixer (in single-point systems) meter CNG into the intake airstream for combustion.

  3. What is the purpose of the manual shutoff valve on a CNG cylinder?

    Answer: To allow manual isolation of gas flow for service or emergency

    The manual shutoff valve lets technicians or emergency responders manually stop gas flow from the cylinder for safety or maintenance.

  4. What type of sensor is used to detect CNG leaks inside a vehicle enclosure?

    Answer: Methane or combustible gas sensor

    Methane sensors or combustible gas detectors are used to detect CNG leaks because methane (CH4) is the primary component of natural gas.

  5. During a fast-fill at a public CNG station, why may the displayed fuel gauge reading drop shortly after fueling ends?

    Answer: Gas cools and contracts after the fast-fill heat of compression dissipates

    Fast-fill compresses gas rapidly, raising its temperature and pressure; as the gas cools to ambient temperature, pressure and the gauge reading drop slightly.

  6. Which regulation governs the design and testing of CNG cylinders used on vehicles in the United States?

    Answer: ANSI/CSA NGV2

    ANSI/CSA NGV2 (Natural Gas Vehicle Cylinder Standard) sets the design, testing, and performance requirements for CNG vehicle cylinders in the U.S.

  7. What is the function of the CNG fuel filter in the low-pressure side of the fuel system?

    Answer: Removes water and particulates that could damage injectors or the mixer

    The low-side filter removes moisture and fine particulates from CNG to protect sensitive components like injectors and the regulator.