On April 20, 2000, about 0620 hours Pacific daylight time, a Schweizer G-164B, N3629F, owned and operated by Haley's Flying Service, Inc., Tracy, California, experienced a total loss of engine power during a positioning flight near Lodi, California. The commercial pilot made a forced landing in a field, collided with a concrete drainage ditch, and nosed over. The airplane was substantially damaged, and the pilot sustained a minor injury. Visual meteorological conditions prevailed, and no flight plan was filed. The flight was performed under 14 CFR 91, and it originated from Tracy, California, about 0615. The pilot reported that he was flying about 800 feet above the ground. He was heading toward an auxiliary strip when the engine lost all power, surged to full power, and then quit completely. The pilot attempted to land in a nearby small field but was 10 to 15 feet short and impacted the dirt berm. The airplane's logbook indicated that it had a total time of about 13,085 hours since new. This current engine was installed in 1997. It had a total time of about 8,180 hours, and 1,237 since last major overhaul. A Federal Aviation Administration airworthiness inspector responded to the accident site and examined the airplane. No evidence was observed of any mechanical problems with the airframe. The ignition and "P" lead were found to be operational in field testing. About 45 gallons of fuel were observed in the center main fuel tank. The engine and damaged engine-related accessories were subsequently examined. The carburetor was observed destroyed in the impact and was not functionally testable. The operator verbally reported to the National Transportation Safety Board investigator that no evidence of any internal mechanical malfunction was found within the engine, and it was returned to service.