What is the purpose of the fuel vapor return line?

The purpose of the fuel vapor return line is to manage the vapors formed in the fuel system, particularly those that can develop in the fuel pump. When fuel is subjected to pressure and temperature changes, vapor can form. The fuel vapor return line allows these vapors to be routed back to the fuel tank, helping to maintain proper fuel system pressure and prevent the accumulation of vapor in the fuel lines. This process is essential for maintaining engine efficiency and preventing issues such as vapor lock, where vapor formation can disrupt the fuel flow to the engine. By returning vapors to the fuel tank, the system prevents potential operational problems and supports the overall reliability of the engine performance.

This answer highlights the function and significance of the vapor return line in the context of a vehicle's fuel system management.