PURPOSE: To prevent the dilution of a lubricant and correctly measure the fuel pressure when an engine is stopped by providing a cutoff valve at the connection piping portion between a fuel main pipe and a fuel feed pump, and incorporating a stop pressure relief valve in the cutoff valve.

CONSTITUTION: A cutoff valve 10 opened by the discharge pressure of a fuel feed pump 6 at the pressure value lower than the preset pressure value of a pressure regulating valve 12 is provided at the connection piping portion between a fuel main pipe 3 and the fuel feed pump 6. A stop pressure relief valve 35 opened by the fuel oil pressure of the fuel main pipe 3 when an engine is stopped at the pressure value lower than the preset pressure value of the cutoff valve 10 is incorporated in the cutoff valve 10. The head pressure of a fuel tank 15 is prevented from being applied to a fuel injection pump 2 when the engine is stopped and the fuel cutoff valve 10 is closed. The pressure of the fuel main pipe 3 or the like is quickly reduced to 0 by opening the relief valve 35. The fuel oil is prevented from leaking and mixing with the lubricant, and the dilution of the lubricant can be prevented.