Gasoline Engine Parts & Definitions

by Paul Dohrman

Gasoline engines use small, sudden gasoline explosions to drive pistons that the crankshaft turns into rotary motion. Gasoline engines mix fuel and air before entering the cylinder, then ignite it by a spark in the cylinder--as opposed to diesel engines, which inject them at different times and ignite by compression.


The carburetor mixes air and gasoline in the proper proportion before it is injected into the cylinder as a mist.

Fuel Injector

Fuel injectors, which are electronically controlled valves, have fully replaced carburetors as the method of mixing gasoline and air. They use an electronic management system, injecting precise amounts of gas depending on sensor readings of engine speed and other conditions.


The ignition of the gasoline in the cylinder pushes a piston outward to crank the crankshaft. The piston oscillates back and forth within the cylinder.

Spark Plug

The spark plug ignites the gasoline, producing the explosion in the cylinder. Old spark plugs can impair ignition timing and, therefore, fuel efficiency.


The camshaft is the shaft with varying radii that pushes against the spring-loaded exhaust and intake valves to the cylinder in order to open them.


Connecting rods attach the pistons to the crankshaft. The crankshaft, the main rotating shaft in the engine, converts the linear oscillations of the pistons into rotary motion.

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