On March 19, 1998, at 1450 hours Pacific standard time, a Cessna 210K, N8274M, lost engine power after takeoff and made an emergency landing on a dirt road near Fallon, Nevada. The airplane, operated by Fallon Airmotive, Inc., under 14 CFR Part 135, sustained substantial damage. The commercial pilot and four passengers were not injured. Visual meteorological conditions existed for the on-demand air taxi flight that was scheduled to terminate at the Reno, airport. The pilot reported that while waiting for his passengers to arrive, he performed the preflight inspection, which included checking the engine oil level. He stated that he added 1 quart of oil. During the takeoff roll, the pilot monitored the airplane's systems, including the engine oil temperature and pressure gauges, and they appeared to be normal. He stated that after takeoff, he initiated a turn to the south, and monitored the tachometer as he reduced the propeller rpm. The pilot reported that the tachometer dropped to zero rpm, but that the engine still sounded normal, and he decided to return to the airport for a precautionary landing. The pilot stated that as he made a 120-degree turn, the engine began to run rough. He pushed the throttle, propeller, and mixture full forward and switched fuel tanks from the right to the left. He was unable to make the airport and landed on a road. The left landing gear touched down on the road, but the right main gear struck a berm. The nose gear was sheared off and the airplane veered off the road. The pilot reported that he turned off the fuel and master switch, and he and his passengers exited the airplane without further incident. A Federal Aviation Administration (FAA) inspector, who examined the airplane on scene, found metal particles in the engine oil and sump, and the engine oil pump appeared to be inoperative. He further stated that the number one cylinder barrel and connecting rod exhibited a blue color, which he attributed to being exposed to high temperatures. A postaccident investigation conducted by the FAA revealed a brass colored substance on the gear and in the screen area of the oil pump. The FAA inspector stated that the driven gear requires two bushings. He reported that he did not find the required bronze bushings installed in-between the driven gear and shaft. He further noted that the driving gear was transversely fractured approximately 2/3 down the splines, and exhibited torsional twisting and a bluing discoloration. A representative from Drake Air, Inc., the facility that overhauled the oil pump housing, stated that if the oil pump is sent as a complete unit for a pump housing overhaul the individual components are placed in a bag and identified as being a part of that particular oil pump housing. Drake Air, Inc. further stated that a disclaimer is placed with the components that states that the components in the bag were not inspected and returned as is. Once the oil pump housing has undergone overhaul, it is delivered to the individual/company that sent it as a disassembled unit. It is the responsibility of a certified airframe and powerplant (A&P) mechanic to reassemble and install the oil pump on the powerplant. Examination of the logbooks revealed that a major overhaul was performed on the engine in November 1997, and at that time the oil pump was shipped to Drake Air for overhaul. The mechanic, who signed off the annual inspection in the airplane and engine logbooks, stated that the owner of the airplane, who is not a certified mechanic, had reassembled the oil pump and installed it on the engine. The mechanic further stated that the oil pump was not properly inspected by a certified mechanic prior to being returned to service. Examination of the logbooks revealed that the airplane had been operated for 162 hours before the accident flight. According to the pilot, who was interviewed by the FAA, he had reassembled the oil pump unit, and it was not inspected by the mechanic prior to reinstallation on the airplane. During the course of the investigation it was noted that the even though the Drake Air oil pump is an FAA-PMA approved part, the engine manufacturer does not approve this part for use on their engines.