The system intended for a pressurized gas engine includes a variable-volume chamber and a valve (1) comprising a first fixed element (3) intended to allow fastening of the valve to the engine, a second moveable element (5) intended to shut off in a conditional manner a passage providing gas communication with the variable-volume chamber, and first elastically deformable coupling means (9) connecting the first and second elements together, the chamber additionally comprising means for operating the second and third moveable elements of the valve.