PURPOSE: To ensure the positive operation of a relief valve by installing this relief valve in a passage connecting a cold fuel sump to a fuel tank, in a device which feeds the cold fuel sump with fuel at the time of clockwise rotation of a motor primer pump and also feeds an intake passage with the fuel of this cold fuel sump at the time of counterclockwise rotation of the pump.

CONSTITUTION: Prior to engine starting, when a primer pump C is driven clockwise, in the case where a constant pressure fuel chamber 38 is empty, air and fuel vapor are inhaled in the pump C by way of a passage 23 of the like, and fed to a cold fuel sump 29 via a passage 28. Fuel in a fuel tank 78 is drawn in the constant pressure fuel chamber 38 with decompression in the constant pressure fuel chamber 38 and thus supplied. Next, when the pump C is rotated counterclockwise, the fuel of the cold fuel sump 29 is drawn in the chamber and fed, under pressure, to a lower empty part 19 of a throttle valve 8 by way of a passage 26 or the like, whereby it is drawn in an intake passage 11 with starting operation of the engine. In this case, a diaphragm type relief valve D is interposingly installed between passages 30, 31 connecting the cold fuel pump 29 to a fuel tank 78, with this constitution, the positive relief operation is made so as to be ensurable.