On December 26, 1998, about 1436 eastern standard time, a Piper PA-28-180, N32679, registered to JKJ Aviation LLC, crashed while making a forced landing following loss of engine power, at Knoxville, Tennessee, while on a Title 14 CFR Part 91 personal flight. Visual meteorological conditions prevailed at the time and an instrument flight rules flight plan was filed. The aircraft received substantial damage and the private-rated pilot and one passenger received serious injuries. The flight originated from Orlando, Florida, the same day, about 0954. The pilot stated he departed Orlando en route to Jackson, Michigan, with a planned fuel stop in Knoxville. The fuel tanks were full with 48 gallons of usable fuel at departure. Experience dictated the aircraft consumed between 8.5 and 9 gallons per hour and he calculated he had about 5 hours 20 minutes of fuel. He stated that the aircraft consumed about 9 gallons of fuel per hour on the flight from Michigan to Florida. As he approached Knoxville, a planned fuel stop, he switched to the right fuel tank, where he estimated 40 minutes of fuel remained. He also estimated he had 40 minutes of fuel remaining in the left fuel tank. After about 10 minutes he saw the fuel pressure drop and he immediately switched back to the left fuel tank. He had no confidence of the fuel remaining in the left fuel tank. He notified air traffic control and asked for them to get him down. He was given radar vectors directly to the airport. While descending through clouds the fuel pressure dropped again. The engine quit a short time later. He switched back to the right fuel tank, the engine restarted, ran a short time, and then quit again. At this point he was too low to attempt any turns. He stalled the aircraft over trees and when the nose dropped, he attempted to guide the aircraft between several homes. The pilot stated he was operating the engine at 70 percent of rated power. He stated he leaned the fuel mixture by moving the engine mixture control toward the lean position until the engine began to run rough. He then moved the engine mixture control toward the rich position until the engine roughness stopped and then moved toward rich a little more. Postcrash examination of the aircraft at the crash site was conducted by an FAA inspector. The fuel tanks were empty, there was no apparent damage to the aircraft's fuel system, and there was no fuel spillage from the aircraft on the ground. All flight controls were functional. The propeller blades were bent aft about 80 degrees. (See the FAA Inspector Statement attached to this report) Postcrash examination of the engine was performed by an NTSB investigator and representatives from Lycoming Engines and Piper Aircraft. The engine was partially separated from the aircraft due to impact forces. The engine throttle linkage and mixture control linkage separated from the carburetor due to impact forces. The engine rotated when turned by hand and each cylinder produced compression. Continuity of the valve train, crankshaft, camshaft, and accessory drive gears was confirmed. The magnetos were timed to the engine at 25 degrees before top dead center. Each magneto fired when rotated by hand. Each spark plug had gray colored combustion deposits. The air inlet filter was clean and the air box was free of obstructions. Examination of the engine fuel system components showed no evidence of fuel stains on the components or fuel leakage from the components. The carburetor bowl gasket had a fuel stain at the rear of the bowl, about 1/4 of the gasket circumference and dark stains coated the carburetor intake throat and the throttle valve. The two carburetor bowl securing screws adjacent to the mixture control were found loose. The remaining securing screws were tight. The float was found to have no leakage and all ports were unobstructed. The inlet fuel screen was free of debris. The engine-driven fuel pump actuated normally. (See the Lycoming Engine Report attached to this report)