A fluid displacement device (200), particularly for use of the device (200) to pressurize balloon catheters, or the like. The device (200) includes a plunger (238) which is displaceable through a housing (208), and an actuating mechanism (246) which engages the plunger (238). The actuating mechanism (246) includes a nut member (204) that is biased into engagement with a threaded portion (279) of the plunger (238). The device (200) has a press-to-release feature wherein the plunger (238) is instantly releaseable by simply depressing a toggle lever (280) of the nut member (204) to overcome a restorative spring force. Subsequently, the plunger (238) can be translated using macro movements (i.e., by pushing or pulling the plunger (238)).
