At 0330 eastern time, a Cessna 182H suffered a total loss of engine power about seven miles northeast of the Knoxville Downtown Island Airport and was substantially damaged in the ensuing forced landing. The pilot and passenger were not injured. The flight departed Auburn, Ala. about two and a half hours earlier on a VFR flight plan. Instrument conditions prevailed at the accident site. The pilot reported that the engine lost power and then during the forced landing to a field the airplane collided with a fence, separating the right wing from the fuselage. A post-crash examination discovered that the left fuel cap was missing and there was blue streaking along the left wing and left side of the fuselage.