On September 27, 1995, at 2034 central daylight time (cdt), a Cessna T210M, N7660E, was substantially damaged following a partial loss of engine power and subsequent forced landing on a field in Dodge City, Kansas. The airplane was on the ILS Runway 14 Approach to Dodge City Regional Airport when the partial loss of engine power occurred. The pilot reported no injuries. The 14 CFR Part 91 flight had departed Springfield, Missouri, at 1817 cdt. Instrument meteorological conditions prevailed at the time of the accident and an IFR flight plan was on file. In a written statement, the pilot reported that as the airplane was descending on the initial approach segment of the ILS approach, he continued to increase the mixture to full rich. The pilot stated that once the airplane reached the assigned altitude of 4,200 feet MSL, he pushed the throttle forward to add power and level off. "I did not hear or feel any power come on," the pilot stated. The pilot stated he then turned the fuel boost pump ON with the throttle one-half open, but was not able to obtain additional engine power. The pilot stated that the airplane was loosing altitude and airspeed and he realized that it was not going to make it to the airport. The pilot stated that at this time, he focused on making an emergency landing. The airplane landed on a field and sustained substantial damage. Postaccident examination revealed no mechanical abnormalities but the spark plugs were found sooty. The engine was successfully started and it ran up to 1500 RPM. An operational test was performed on the auxiliary fuel pump. During engine operation, the auxiliary fuel pump was switched to the ON position. This resulted in a metered fuel pressure increase, a reduction in engine RPM, and the engine began running rough. Advancing the throttle with the pump ON resulted in a loss of combustion due to fuel flooding. The fuel pump was then turned to the OFF position. The engine RPM decreased and the engine re-ignited. See attached copy of report. The Normal Procedures Section of the Pilot's Operating Handbook for the Cessna 210 recommends the following procedure for a descent: "power as desired, auxiliary fuel pump OFF, mixture adjust for smooth operation, and cowl flaps closed." The pilot stated to the FAA and to a representative of the airplane manufacturer that he always turns the auxiliary fuel pump ON during all approaches.