At approximately 1600 central time, a Piper PA-28 was substantially damaged following a loss of engine power while landing on a private grass strip. The sole occupant of the airplane, was not injured. According to the pilot, he was on the downwind leg when the engine began to run rough. The pilot advanced the throttle, however the engine continued to run rough. The aircraft landed in heavy brush, approximately 150 yards short of the runway. An FAA inspector who inspected the accident site reported that the fuel pump circuit breaker was tripped.