An exhaust check valve and piston return system wherein a main exhaust valve is opened as a result of combustion products from the combustion chamber being routed through a signal line. In addition, as a result of the opening of the main exhaust valve, an exhaust check valve, incorporated within a side wall portion of the cylinder housing at a location disposed downstream of the main exhaust valve, as considered in the direction of flow of the exhaust gases out from the combustion chamber, is forced to its open position so as to permit the combustion gases to be exhausted from the combustion chamber, thereby permitting the piston to move upwardly so as to complete its return stroke.