What happened
During cruise flight, the Cessna (type not specified in source) experienced a complete loss of engine power following an engine fire. The pilot reported that preflight and takeoff procedures were normal. While flying at approximately 1,100 feet above ground level to remain below Class B airspace, the pilot activated the standby vacuum pump and confirmed it was operating correctly. Within one to two seconds of activating the pump, the alternator annunciator light illuminated. Shortly thereafter, two passengers reported smelling something burning. Approximately two seconds after the light appeared, the engine abruptly lost power without any preceding roughness or surging. The pilot subsequently executed a forced landing into a river, resulting in substantial damage to the aircraft. There were no fatalities reported.
The investigation
An examination of the engine compartment identified an area of heat and fire damage near the top of the engine. Investigators found bare wires on the P-leads within this damaged area. Testing of the magnetos revealed that the P-leads were grounded, preventing electrical current from reaching the magnetos. Further inspection of the engine found a loose B-nut fuel line connector on the line running from the engine-driven fuel pump through the engine baffling. This loose connector was located adjacent to the burned area where the P-leads had been damaged. The fuel line in question was positioned directly above the standby vacuum pump. Engine logbook records indicated that the oil, oil filter, and standby vacuum pump had all been replaced prior to this flight.