The pilot stated that he filled the airplane's fuel tanks with full fuel prior to departing on the cross-country flight. Approximately 30 minutes into the flight, at an altitude of 3,000 feet above ground level, the engine suddenly stopped producing power. The pilot checked the fuel mixture and fuel selector settings and attempted to restore engine power but was unsuccessful. He maneuvered the airplane for a forced landing in a field and landed with the gear in the retracted position, resulting in substantial damage to the airplane's fuselage. Postaccident examination of the engine compartment by a Federal Aviation Administration (FAA) inspector revealed that the flexible fuel hose that connects to the inlet fitting of the servo fuel injector was separated from the inlet fitting. No damage to any portion of the fitting or to the B-nut, or to the threads of the fitting or B-nut was noted, and there was no evidence of torque seal putty on the B-nut. There was no provision for safety wire to secure the B-nut. The most recent annual inspection was performed approximately 7 flight hours since the inspection. The mechanic who performed the annual inspection stated to an FAA inspector that he did remove the separated line during the inspection to gain access to the fuel inlet screen. He further stated that about the time of the inspection he incorporated a process of applying purple colored torque seal putty on components that he disassembled or removed.