On February 20, 1995, about 1100 eastern standard time, a Hughes 500C, N7172Z, registered to Flying Gophers Inc., operating as a 14 CFR Part 91 personal flight, experienced a reported total loss of engine power in cruise flight in the vicinity of Key Largo, Florida. A forced landing was made on a public highway. Visual meteorological conditions prevailed and no flight plan was filed. The helicopter sustained substantial damage. The commercial pilot was not injured. The flight originated from Opa Locka Airport, Opa Locka, Florida, about 45 minutes before the accident. The pilot stated he was at 500 feet agl when he observed a high reading on the power turbine governor. He decreased the governor with the governor rpm switch and continued with the flight. About 1 minute later the helicopter experienced a total loss of engine power. The helicopter yawed to the left, followed by the illumination of the engine out warning light and engine out audio. He entered autorotation towards a highway. At 100 feet he initiated a deceleration and applied initial collective pitch at about 20 feet. Cushioning collective pitch was not applied. The helicopter collided with the ground ventral fin first, rocked forward, and slid about 150 feet before coming to a complete stop. An engine fuel and pneumatic system check was performed by McDonnell Douglas Field Service Representative under the supervision of the FAA on March 7, 1995. The fuel system failed the vacuum check. The hose assembly from the before filter (BF) port was loose at the fuel pressure switch after filter (AF) coupling B-nut of the engine-driven fuel pump. The engine was removed and transported to an authorized repair facility in Miami, Florida, for an engine test run. Before testing, it was noted that about 9cc of fuel was present in the engine-driven fuel pump filter bowl; an additional 1cc of fuel was present in the fuel nozzle inlet line. The coupling B-nut was tightened. The engine was run in a test cell on March 8, 1995, in the presence of the NTSB investigator-in-charge, and parties to the investigation. The engine started, ran, and developed adequate power. The AF filter side coupling B-nut of the fuel pressure differential switch was loosened 1 1/2 turns and the engine shut down.