FAA Powerplant Written Practice Test

What is one potential issue if a two-stroke engine overheats?

1. The spark plugs will need to be replaced

2. The engine may run even with the ignition turned off

3. The battery will discharge faster

4. Oil may leak from the crankcase

The correct answer is: The engine may run even with the ignition turned off

In a two-stroke engine, overheating can lead to a variety of problems due to the design and operation of the engine. One significant issue that can arise when a two-stroke engine overheats is that it may continue to run even when the ignition is turned off. This phenomenon is often referred to as "dieseling" or "run-on," which can occur because the high temperatures can ignite the fuel mixture in the combustion chamber without the need for a spark from the spark plug. The inherent design of a two-stroke engine, which mixes oil with fuel, can contribute to this issue as well. If the engine overheats, residual heat may allow unburned fuel to ignite spontaneously. Consequently, this results in the engine continuing to run despite the ignition being switched off, leading to potential damage from uncontrolled operation. Understanding the dynamics of two-stroke engines and their cooling requirements is crucial for anticipating and mitigating such complications. While other options mention concerns like spark plugs needing replacement, battery discharge rates, or oil leaks, they do not directly relate to the immediate mechanical and safety risks introduced by overheating in a two-stroke engine.