PURPOSE: To make gold start easier by controlling and supplying fuel to a carburetor only at a particular time corresponding to the engine temperature at the priming operation in a small sized internal combustion engine suitable for a chain saw.

CONSTITUTION: A pump 14 has a bellows 18 pressed by a spring 20, a ball 22 cooperates with a reverse valve 24 to supply and to purge fuel. A pin 26 connected to the bellows 18 engages with a switch 28 to detect the fill of the fuel. Furthermore, while an inlet of the pump 14 is connected to fuel reservoir 34 through a carburetor 32, an outlet of the pump 14 is connected to the fuel reservoir 34 through a solenoid valve 16 and an orifice 40. On the other hand, the solenoid valve 16 is connected to a nozzle 42 located at air intake 44 of the carburetor 32 arranged between the carburetor 32 and air filter 46. The solenoid 16, switch 28, temperature sensor 50 and battery 52 are all connected to the priming control electronic circuit 30.