What is the role of a fuel return line in older injection systems?

• A. Delivers additional fuel to injectors
• B. Returns excess fuel to the tank to regulate pump pressure and aid cooling
• C. Vents vapors to atmosphere
• D. Feeds fuel to the heater

Answer: (B)

The fuel return line keeps fuel pressure stable and helps cool the pump by circulating excess fuel back to the tank. In older injection systems, the pump pushes fuel through a regulator that maintains the needed pressure at the injectors. Any surplus fuel is routed back via the return line to the tank, so the system doesn’t over-pressurize as engine conditions change. That constant circulation also removes heat from the pump, which helps prevent overheating and vapor formation. This line isn’t about delivering fuel to injectors, venting vapors, or feeding a heater.