Massachusetts Hoisting License Practice Test

How does the fuel in a gas engine ignite?

1. Air combustion caused by spark

2. Compression ignition

3. Heat from the engine

4. Catalytic reaction

The correct answer is: Air combustion caused by spark

In a gas engine, ignition of fuel occurs when an air-fuel mixture is compressed and then ignited by a spark produced by the ignition system. The process begins with the intake of air and fuel into the combustion chamber, where they mix. During the compression stroke, the piston moves up, compressing this mixture, and as the compression reaches its peak, the spark plug emits a spark that ignites the compressed air-fuel mixture. This ignition produces a rapid expansion of gases that pushes the piston down, creating the power needed to drive the engine. The first response accurately describes the ignition process by emphasizing the critical role of the spark generated by the spark plug in that specific type of engine. Other types of engines, like diesel engines, operate using compression ignition instead, which relies solely on the high pressure and temperature to ignite the fuel without the need for a spark. Therefore, the mention of air combustion caused by spark reflects the fundamental operation of a gas engine and its reliance on an electrical spark for ignition.