On May 19, 2000, at 0955 mountain daylight time, a Cessna 172XP, N758SZ, sustained substantial damage during a forced landing near Kelly Air Park (U38), Larkspur, Colorado, when it nosed over on landing roll. The certified flight instructor and student pilot were not injured and no flight plan was filed for this instructional flight operating under Title 14 CFR Part 91. The flight departed Centennial Airport, Englewood, Colorado, at 0900. Visual meteorological conditions prevailed. According to the flight instructor, he reduced power to "just above" idle approximately 2,000 feet above ground level (agl) and was having his student practice an engine out approach. The student set up for approach to an open field and the flight instructor said he checked the engine once during the glide, which was described as being in excess of 2 miles. When the student added power at the termination of the approach, the engine failed to respond. The instructor said he took control of the aircraft and decided to land in the field the student had picked during practice. The field was soft and muddy and during landing roll, the nose landing gear dug in and the aircraft nosed over causing substantial damage to the wings, fuselage, and empennage. Examination of the aircraft/engine provided no evidence of an airframe or engine abnormality. It did provide evidence that the fuel boost pump had been improperly wired so that it operated in high if either the "low" or "high" on position was selected. When the wiring was done was not established, and the mixture setting being used by the pilot was also not established. The boost pump switch was found in the "low" position as prescribed for the maneuver being conducted. The closest weather reporting station, approximately 10 miles from the accident site, recorded a temperature of 82 degrees Fahrenheit and a dew point of 55 degrees Fahrenheit during the time period when the accident took place.