On November 18, 2022, about 0745 eastern standard time, a Piper PA28-181, N8129M, was substantially damaged when it was involved in an accident near Manassas, Virginia. The flight instructor and a student pilot were not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 instructional flight. The flight instructor and student were preparing for a flight at Manassas Regional Airport/Harry P. Davis Field (HEF), Manassas, Virginia. The flight instructor reported that he primed the engine with fuel several times and attempted to start the engine in the cold weather; the engine got close to starting but did not maintain power and stopped. He attempted another start with the same result. After waiting several minutes, he primed it once and attempted to start it again, but it shut off after about 4 seconds. During the fourth attempt, he did not use any primer, but white smoke started emanating from the engine compartment. He shut off the fuel valve and electrical equipment and then grabbed the fire extinguisher before exiting the airplane. The smoke continued to increase and a mechanic who was nearby told him to aim the fire extinguisher into the engine air intake and attempt to suppress any developing fire; he did so to no effect. The smoke continued to increase in severity followed quickly by fire emanating from the engine compartment. The fire increased in intensity and engulfed the front of the airplane in about 5 minutes before airport fire rescue services arrived and extinguished the fire. A Federal Aviation Administration (FAA) inspector examined the wreckage. The fire consumed the engine compartment and entire cockpit and cabin. There was additional thermal damage to the wings. Further examination revealed electrical arcing damage to the alternator wire. Electrical pitting was discovered on the engine mounts and the alternator wire displayed features consistent with electrical arcing. The clamp that affixed the wire was severely damaged and melted and appeared to be oversized. There was damage to the wire and clamp where they joined and was in close proximity to a fuel line. A review of maintenance records for the preceding 36 months did not yield any items associated with the alternator or wires.