What is the function of check valves in fuel systems?

• A. Limit fuel to one direction
• B. Regulate pressure in tank
• C. Allow venting of fuel vapor
• D. Direct fuel to engine

Answer: (A)

Check valves in fuel systems act as one-way gates. Their job is to let fuel flow toward the engine but block any flow in the opposite direction. This prevents fuel from draining back into the tank or back through other components when pressure changes or the pump cycles off, helping keep the system primed and the engine fed with fuel. They don’t regulate pressure—that’s a regulator’s job—nor do they vent fuel vapors—that’s handled by venting systems. They also don’t directly direct fuel to the engine; they simply enforce the correct direction of flow.