On July 11, 1998, at 0925 central daylight time, a Vollmers Sonerai II L (amateur built airplane), N317WM, impacted the terrain during a forced landing after loss of engine power. The private pilot received minor injuries and the airplane sustained substantial damage. The pilot stated he was descending to land at Bismarck Municipal Airport when the airplane lost power. The airplane was being operated as a personal flight under 14 CFR Part 91 when the accident occurred. Visual meteorological conditions prevailed at the time and no flight plan was filed. The flight originated in Jamestown, North Dakota at 0845. The pilot said that he did not know why the engine lost power. He said in his written statement that after the loss of power, he attempted to land on a dirt road landing to the north; however found the wind to be from the south. He attempted to make a low level turn to land more into the wind, but temporarily lost control of the airplane. When he regained control the airplane touched down in a ditch and after rolling a "few hundred feet," nosed over. An examination of the engine subsequent to the accident revealed a corroded wire in the electronic ignition system. There was no spark available to the spark plugs. The ignition system on the engine was an automotive installation on this amateur built airplane.