PURPOSE: To prevent the useless consumption of the lubrication oil by forming the main and the slow systems independently while making the mixing ratio of the lubrication oil in the fuel in the slow system lower than that in the main system.

CONSTITUTION: The main system port 6 opening to a suction path 3 and the fuel system conducting to the slow system port 12 are formed independently. A main system float chamber 7, main system fuel pump 10 and a main system fuel tank 11 are coupled to the main system port 6 while a slow system float chamber 13, slow system fuel pump 14 and a slow system fuel tank 15 are coupled to the slow system port 12. The content of the lubrication oil mixed in the fuel in the system fuel tank 15 is made lower than that in the main system fuel tank 11.