Does the fuel pump relay switch affect mpg?

Yes, a faulty fuel pump relay can affect MPG. A fuel pump relay is a type of electrical switch that controls the fuel supply to the engine. It is responsible for turning on the fuel pump when the engine is running and turning it off when the engine is off. If the fuel pump relay is not working properly, it can cause the engine to run rich or lean, which can lead to decreased MPG. Additionally, a faulty fuel pump relay can cause the engine to stall or hesitate, which can also lead to decreased MPG.