What best describes vapor lock in a fuel system?

Vapor lock is best described as a condition where fuel bubbles form and restrict the flow of fuel in the system. This situation occurs typically when the fuel temperature rises to a point where it vaporizes, creating gas bubbles in the fuel lines or fuel pump. These vaporized bubbles can obstruct the normal flow of liquid fuel to the engine, leading to performance issues such as hard starting, stalling, or a complete failure to start. This phenomenon is more common in hot weather conditions or when engine temperatures are high, as it can cause the volatility of the fuel to increase.

Understanding vapor lock is crucial for managing fuel system issues in four-stroke engines, especially since it can impact engine performance and reliability. It is important for technicians and operators to recognize the signs of vapor lock to prevent potential engine failures and to ensure that the fuel system operates efficiently.