Abstract: An internal combustion actuated fastener driving device in which a simple container supply of fuel under pressure carried in a handle portion of the portable housing assembly feeds to a supply chamber controlled by an actuating valve operable in response to a manual acuating procedure to be spring moved into an operative position. The movement of the actuating valve into its operative position communicates a previously formed charge of gaseous fuel under pressure in a separate charge chamber with a series of nozzles so as to discharge in jet stream formations which aspirate fresh air through inlets to mix therewith in a mixing chamber for passage into a combustion chamber in open condition controlled by a main valve. The main valve moves under spring bias into a closed position in response to the depletion of gaseous fuel pressure within the charge chamber in timed relation with the crowding of the spent gases from the combustion chamber by the new combustible mixture.