Which of the following significantly affects the performance of a fuel system through vapor lock?

Vapor lock occurs when the fuel in a system transitions from a liquid to a vapor at an undesired point, often due to elevated temperatures. This phenomenon can significantly hinder the performance of the fuel system, as it interrupts the flow of fuel to the engine. When temperatures are high, the fuel can vaporize within the lines, especially in areas where there is little cooling or where the fuel system is exposed to heat sources.

In a four-stroke engine, maintaining a consistent state of liquid fuel is crucial for optimal performance and efficient combustion. When fuel vaporizes before reaching the engine, it can lead to a loss of fuel pressure, causing the engine to stall or run poorly. This is particularly problematic when operating under high temperature conditions, making temperature the most impactful factor contributing to vapor lock issues in fuel systems.