On June 25, 1999, at 1030 hours Pacific daylight time, a Cessna TU206F, N8728Q, experienced a loss of engine power and collided with ground obstructions during the subsequent forced landing in an open area in Saline Valley, California. The accident site is about 50 miles southwest of Bishop, California. The aircraft, owned and operated by the pilot, sustained substantial damage. The private pilot and three passengers were not injured. The personal cross-country flight, conducted under the provisions of 14 CFR Part 91, originated from the Bishop Airport earlier the same morning, stopped at the Boulder City, Nevada, airport, and departed about 0945 en route back to Bishop. Visual meteorological conditions prevailed and no flight plan was filed. The pilot reported that he took off from Bishop with full fuel tanks (80 gallons). He estimated that each leg of the flight lasted approximately 1 hour 25 minutes. He further estimated that with full tanks of fuel, the aircraft's endurance was about 5 hours 20 minutes, with a fuel burn of about 15 gallons per hour. He stated that during his preflight in Boulder City, he noted that the strainer valve seemed to be binding and stuck after he drained fuel from the main fuel sump. The pilot reported that he took off with the fuel selector positioned to the right tank, but he later noticed that the left and right fuel gauges were both indicating decreasing amounts of fuel. He reported that the right fuel gauge dropped to "empty" and the engine suddenly quit. The pilot stated that when he switched the fuel selector to the left tank and turned on the boost pump, the engine started back up. He stated that the engine ran for about 3 to 4 minutes before quitting again. He set up an approach to a dirt road located in a canyon, but came in too high and fast. The pilot reported that he forced the airplane down to the road and applied full brakes after landing. The aircraft impacted an embankment that was slightly higher than the wings. Both wings, the nose gear, and part of the tail collided with the terrain. The nose gear sheared off. The pilot reported that after the accident, he noted a small amount of fuel on the ground underneath the main fuel sump. He stated that it looked like the strainer valve had been stuck in the open position, which allowed the fuel to drain out. A Federal Aviation Administration inspector from the Las Vegas Flight Standards District Office responded to the accident site. He reported that he didn't find any mechanical discrepancies with the airplane. According to the Cessna TU206F Pilot's Operating Handbook, fuel cannot be used from both fuel tanks simultaneously. A representative from Cessna reported that if the strainer valve had been stuck open, fuel would drain out only from the tank selected on the fuel selector valve. The Cessna TU206F fuel system schematic confirms that the fuel strainer is positioned after the fuel selector valve. The pilot supplied a copy of a fuel receipt which reflected that the airplane had been topped off with fuel on June 11, 1999. He stated that he did not remember if he had flown the airplane between then and the accident flight; he did not maintain any type of pilot logbook or flight record. The pilot reported that he had not experienced any mechanical problems with the aircraft prior to the accident.