On August 9, 2009, about 1800 eastern daylight time, a Laurienzo Varieze, experimental amateur-built airplane, N808SA, registered to and operated by a private owner, as a Title 14 Code of Federal Regulations Part 91 personal flight, experienced a loss of engine power in cruise flight near North Augusta, South Carolina. The pilot made a forced landing to a highway and collided with power lines and a pole. Visual meteorological conditions prevailed and no flight plan was filed. The airplane received substantial. The private pilot received serious injuries. The flight originated from Twin Lakes Airport (S17), Graniteville, South Carolina, at an undetermined time. The pilot stated he was having problems with “dirt dabbers” getting into the fuel vent, so he decided to correct the problem by installing a rubber cap on the fuel vent system. In addition, he planned on making an entry in the checklist, and adding a red flag to the cap, however he did not do either. On the day of the accident, the pilot stated he conducted a preflight inspection, and failed to remove the black cap from the fuel vent. He departed S17 and was in cruise flight at 2,000 feet mean sea level, paralleling I-20 westbound, when the engine quit. The pilot stated, he immediately knew what happened, and wished he could have crawled outside and removed the black fuel vent cap. "The engine had quit because the air could not enter the fuel tank due to the blocked fuel vent line, which caused the loss of engine power due to fuel starvation." The pilot switched the fuel tank selector from the main fuel tanks to the reserve fuel tank. The engine started and stopped about 30 seconds later. He observed an interstate highway, which was under construction and flew towards it. He lined up with the interstate, lowered the nose landing gear, lowered the flaps to the full down position, and assumed a 90 mph landing to the south. The airplane collided with wires, which the pilot had not seen. The nose of the airplane pitched down, the airplane banked to the right 90 degrees, and he was unable to recover the airplane. The airplane collided with the ground nose down and came to rest inverted. The pilot further stated, "There was nothing mechanically wrong with the airplane. The accident was complete pilot error." Examination of the airplane by Federal Aviation Administration inspectors revealed the fuel vent was blocked with a black cap. No anomalies were noted with the fuel system, engine assembly or associated components.