The airplane was executing a VFR approach, turning from the base leg to short final, when the engine lost total power. During the ensuing forced landing, the airplane touched down in a field short of the runway, the nose landing gear collapsed, and the airplane came to a stop upright. The pilot reported to the FAA that 'he was not sure if the fuel selector was in the detent for the selected tank and he did not have time to check prior to landing.'