Fuel System Components Flashcards

What is the primary function of a CNG pressure regulator in the fuel system?

Answer: Reduce high-pressure gas to a usable engine inlet pressure

The pressure regulator steps down the high storage pressure (up to 3,600 psi) to the low pressure required by the engine's fuel injection system.

Which material is most commonly used for CNG high-pressure fuel lines between the cylinder and the regulator?

Answer: Stainless steel tubing

Stainless steel tubing is used for high-pressure CNG lines because it resists corrosion and can safely handle pressures up to 3,600 psi.

A CNG manual shutoff valve is typically located:

Answer: At the cylinder valve or close to the storage tank

The manual shutoff valve is placed at or near the cylinder to allow technicians to isolate the fuel supply during service or in an emergency.

What does a CNG fuel filter primarily remove from the gas stream?

Answer: Particulates, oil mist, and moisture

CNG filters remove solid particles, compressor oil mist, and water vapor that could damage regulators, injectors, and other precision components.

In a bi-fuel CNG vehicle, the gasoline and CNG fuel systems are connected through:

Answer: A fuel selector switch and dedicated solenoid valves

A bi-fuel system uses a selector switch to open and close solenoid valves, directing fuel flow from either the CNG or gasoline system to the engine.

The pressure relief device (PRD) on a CNG cylinder is designed to:

Answer: Open automatically when cylinder temperature exceeds a threshold

The PRD is thermally activated to vent gas safely if the cylinder is exposed to excessive heat, such as during a vehicle fire, preventing a catastrophic rupture.

Which CNG system component is responsible for delivering precise amounts of fuel into the engine intake?

Answer: CNG fuel injector

CNG injectors are electronically controlled to meter exact fuel quantities into the intake manifold based on signals from the engine control module.