Patent ID: 7789074

Claim:
A fuel supply system for supplying fuel to an internal combustion engine, the fuel supply system comprising: a fuel tank; a delivery pipe connected to an injector that injects fuel to the engine; a main passage that extends to the delivery pipe from the fuel tank; a fuel pump that is provided on the main passage and pressurizes and sends the fuel in the fuel tank to the delivery pipe; a high-pressure return passage that returns excess fuel in the delivery pipe to the fuel tank; a high-pressure regulator that opens the high-pressure return passage when fuel injection pressure in the delivery pipe is a high-pressure threshold value or higher, wherein the high-pressure return passage has an upstream end, a downstream end, and a vertically lower portion, and the upstream end is connected to the delivery pipe via the high-pressure regulator, the downstream end is connected to the fuel tank, and the vertically lower portion is vertically below the upstream end and the downstream end; a low-pressure return passage that returns excess fuel in the main passage to the fuel tank and is connected to the main passage; a low-pressure regulator that opens the low-pressure return passage when the fuel injection pressure is a low-pressure threshold value or higher, wherein the low-pressure threshold value is lower than the high-pressure threshold value; a switch valve that switches an open state and a closed state of the low-pressure return passage; and a control section that controls the fuel pump, the control section controlling the fuel injection pressure by switching the open state and the closed state of the switch valve based on a running state of the engine, wherein, after the engine is stopped, the control section switches the switch valve to the closed state and drives the fuel pump so as to execute a forced return process to cause the fuel to flow into the high-pressure return passage, wherein the control section calculates an accumulated amount of fuel that flows into the high-pressure return passage by the forced return process, and wherein, when determining that the accumulated amount has become a volume of the high-pressure return passage or more, the control section terminates the forced return process.