The invention relates to a fastener driving tool comprising a tank (2) for storing a fluid, in particular liquefied petroleum gas, a combustion chamber (1) connected to the tank (2), wherein the combustion chamber (1) has a movable piston (6) for powering a driving plunger (7), and a metering device (4) arranged between the tank (2) and the combustion chamber (1), wherein the metering device (4) has a movable displacement member (19) for ejecting the fuel out of a metering space (15), wherein the displacement member (19) can be moved by an actuation force from a first power source in a displacement direction against a pressure of the fuel, wherein an additional supporting force from a second power source acts on the displacement member (19).