On November 15, 1996, at 1405 hours Pacific standard time, a Beech 35-33, N961T, collided with a berm during an attempted forced landing near Apple Valley, California. The forced landing was precipitated by a loss of engine power during cruise flight. The aircraft was operated by the pilot, and was on a personal cross-country from Lake Havasu, Arizona, to Apple Valley, California. Visual meteorological conditions prevailed at the time and no flight plan was filed. The aircraft incurred substantial damage. The certificated private pilot, the sole occupant, sustained serious injuries. The flight originated from Lake Havasu at 1230 hours mountain standard time on the day of the accident. The pilot reported that while he was descending toward the Apple Valley airport the engine began to run rough, then quit. He was utilizing the left auxiliary fuel cell at the time, and further reported that he immediately switched to the right main tank, which was the fullest. He was unable to obtain a restart, even by positioning the fuel selector to other tanks. As the aircraft neared the ground he attempted to land on a dirt road, but had insufficient altitude and landed in rough terrain. The aircraft collided with a berm during the landing sequence. Aircraft recovery personnel found about 23 gallons of fuel in the right main tank and 10 in the left auxiliary. Both tanks were leaking fuel at the time. The fuel selector was positioned to the right main tank. A postcrash inspection of the engine and fuel system was conducted by the Safety Board. No discrepancies were noted with the engine. Inspection of the fuel system revealed that the left auxiliary fuel cell vent lines were plugged by insects and mud at two different internal locations.