Some vehicles may exhibit a high-frequency noise from the fuel pump. When the fuel temperature is high, vaporization may occur in the return fuel from the pressure regulator valve assembled on the fuel pump unit. In that situation, the spring in the pressure regulator causes self-excited vibration, resulting in the high-frequency noise. To eliminate this concern, the shape of the pressure regulator valve in the fuel pump has been modified to control self-excited vibration by reducing pressure differences in the valve path.
