On October 1, 1994, at 0900 central daylight time, an Ercoupe 415-C, N99600, piloted by the student pilot/registered owner, experienced a loss of engine power during cruise flight in the vicinity of Cloverdale, Indiana. The airplane sustained substantial damage during the ensuing forced landing on rough terrain. The student pilot, the sole occupant, reported no injuries. Visual meteorological conditions prevailed for the local flight, no flight plan was filed. The flight originated from a private airstrip in Eminence, Indiana approximately 0830. Postaccident examination revealed the header fuel tank was not receiving fuel through the fuel pump from the main fuel tanks. The FAA Inspector stated "...Contamination was found in the restrictor fitting...on the fuel pump. This contamination blocked the orifice...." The contamination was described as a "...hard black piece." The FAA Inspector stated the pilot used automotive fuel in the airplane. The most recent maintenance on the airplane was an Annual Inspection performed June 21, 1994. An FAA Inspector statement is appended.