What can lead to fuel vapor lock?

Fuel vapor lock occurs when the fuel in the lines vaporizes due to high temperatures or insufficient flow, creating gas bubbles that disrupt the fuel supply system. When the fuel system experiences excessive heat—often from the engine or surrounding environment—or there is low fuel flow, the fuel can reach its vaporization point, leading to a blockage in the fuel lines. This prevents the liquid fuel from reaching the engine, resulting in engine performance issues, such as hesitation or stalling.

While high altitude flying can also affect fuel dynamics due to changes in atmospheric pressure, it is not a direct cause of vapor lock in the same way that heat and flow issues are. Fuel contamination can impair fuel quality and engine performance, but it does not directly cause vapor to form in the lines. Similarly, poor engine tuning can lead to operational inefficiencies but does not create the conditions necessary for vapor lock to occur. Hence, the primary factors leading to vapor lock are indeed excessive heat and low fuel flow.