On August 16, 2000, about 1752 Alaska daylight time, a Piper J-3 airplane, N88283, sustained substantial damage when it collided with a parked vehicle during an emergency landing after takeoff from the Merrill Field Airport, Anchorage, Alaska. The solo private pilot received minor injuries. The flight was conducted under 14 CFR Part 91, as a local personal flight. Visual meteorological conditions prevailed at the time of the accident, and no flight plan was filed. The pilot told an NTSB investigator at the scene that about one minute after takeoff, about 500 feet agl, the engine lost total power. He reversed direction to return to the airport, declared an emergency, and attempted to land on a street. After landing, the airplane collided with a parked vehicle at an automobile dealership. The airplane sustained substantial damage to both wings and the fuselage. Postaccident inspection of the carburetor, ignition system, induction and exhaust systems, and fuel supply systems, discovered no preaccident mechanical anomalies. The pilot stated in his NTSB Pilot/Operator Report, and during several interviews, that prior to his departure, he put 6 gallons of fuel in the right tank, and visually checked 8 gallons in the nose, and 5 gallons in the left wing. During his departure from Merrill Field, while about 500 feet agl, he said he closed the fuel valve to the forward fuel tank, and opened the fuel valve to the right wing tank. He stated that 45 seconds after this action, the engine lost power, and the propeller stopped rotating. The pilot indicated that he then opened the left fuel tank valve, and closed the right valve, but the engine did not restart. The airplane is not equipped with a starter motor. The pilot stated that after the accident, at the request of rescue personnel, he ensured the three fuel valves were shutoff to stop any fuel leakage. Within 30 minutes of the accident, an NTSB investigator and an FAA inspector, arrived on scene. The FAA inspector told the NTSB IIC, and wrote in a statement, that he looked into the front tank, and it appeared empty of fuel. A photograph taken at the scene shows the float-operated fuel quantity indicator in the zero fuel position. The carburetor bowl remained intact, and had fuel in it at the scene. Postaccident inspection revealed the center fuel tank did not have a quick drain valve. FAA Airworthiness Directive (AD) 85-06-04, effective May 4, 1985, requires the installation of a quick drain valve in the center (fuselage) fuel tank. The purpose of the AD is, "To prevent engine stoppage or malfunction due to the accumulation of water or other contaminants in the fuel system...). The airplane was modified with the addition of two, wing-mounted fuel tanks, authorized by Supplemental Type Certificate (STC) SA562GL, on September 14, 1994. An addendum to the installation instructions, dated November 21, 1997, requires the installation of a drain valve in the center fuel tank, when the center fuel tank is used in conjunction with the wing tanks. This addendum was not accomplished. The pilot stated that the center tank fuel was normally drained during preflight by using the gascolator fuel line drain. He said he had drained a small amount of water from the center tank prior to the accident flight, and had stopped draining when all evidence of water had ceased. The fuel supply outlet from the center tank is located in the center-bottom of the tank, below the level of the gascolator. The airplane attitude on the ground is about 7 degrees nose up. The NTSB IIC, the FAA inspector, and the owner, determined that when the gascolator is used to drain the center tank, there are two cups of undrainable fluid remaining in the center tank in the normal taxi attitude. In the two-week period prior to the accident, the airplane had been parked outside and exposed to rainfall. The center fuel tank cap was not equipped with a seal, or an "O"-ring. During postaccident testing, it was observed by the NTSB IIC, the FAA inspector, and the owner, that all three-fuel valves worked properly, and when in the closed position, none of the valves leaked when pressurized air was applied to the fuel lines.