Power tool, in particular a hand-held compressed air screw driver

A pneumatic screwdriver or nutsetter includes a manually actuated electrical switch and a solenoid operated motive air shutoff valve which includes a spring biased reset element for moving the shutoff valve closure element from a valve closed position to a valve open position prior to introduction of compressed air to the tool motor. The reset element is retracted away from the closure element by pressure air on startup of a tool operating cycle. The closure element is released upon deenergization of the solenoid at a predetermined signal to close the shutoff valve. In an alternate embodiment the switch is replaced by a pneumatic valve and the reset element is pressure air biased to move the shutoff element from the shutoff valve closed position to the open position.