On July 4, 1999, at 0923 central daylight time, an Ercoupe 415-CD, N127G, registered to and operated by a private pilot, sustained substantial damage during a forced landing following loss of engine power near Jacksonville, Illinois. The pilot reported no injuries. The personal 14 CFR Part 91 flight was operating in visual meteorological conditions. No flight plan was on file. The flight departed Jacksonville Airport at 0912, with the stated destination of Grand Rapids, Michigan. The pilot said that the airplane was climbing through 2,000 feet mean sea level when the engine encountered a loss of power. He said that he conducted a forced landing in a cornfield, at which time the airplane sustained substantial damage. An inspection of the airplane subsequent to the accident found material in the fuel line between the header tank and gascolator blocking the flow of fuel. The material was the consistency of sloshing compound also found in the fuel tank. No record could be found indicating when the tank was sealed with sloshing compound. The most recent annual inspection was conducted on October 19, 1998. The airplane had accumulated 32 hours time in service since that inspection.