What does a compression test evaluate in an engine?

A compression test evaluates the pressure generated in each cylinder of an engine. This test involves cranking the engine and measuring the maximum pressure that builds up in each cylinder during the compression stroke. High compression readings indicate that the piston rings, cylinder walls, and valves are in good condition, allowing for proper sealing and efficient combustion. Conversely, low compression readings can signal issues such as worn or damaged piston rings, leaking valves, or head gasket failures, which can lead to poor engine performance, reduced power, and increased emissions.

The other options focus on different systems within the engine. The efficiency of the fuel system pertains to how well fuel is delivered and atomized for combustion, while the condition of the exhaust system relates to the expulsion of gases and back pressure. The performance of the ignition system involves the ability to create and deliver a spark for combustion. Each of these components plays a crucial role in overall engine function, but a compression test specifically targets the internal sealing and pressure dynamics within the cylinders.