Abstract: An apparatus for injecting fuel into an engine through fuel injectors connected to a fuel tank through a fuel supply passage having a fuel pump provided therein. The apparatus include a first pressure regulator provided in the fuel supply passage between the fuel pump and the fuel injectors for varying the amount of excess fuel returned through a first return passage to the fuel tank to maintain a first predetermined pressure differential across the fuel injectors. The apparatus also includes a second pressure regulator provided in the fuel supply passage downstream of the fuel injectors for varying the amount of excess fuel returned through a second return passage to the fuel tank to maintain a second predetermined pressure differential across the fuel injectors. The second predetermined pressure differential is higher than the first predetermined pressure differential. A control valve is provided in the first return passage.