On March 27, 2016, about 1100 eastern daylight time, a Piper PA28-180, N16366, was substantially damaged after a fire occurred during engine startup while the airplane was parked on the ramp at the Allegheny County Airport (AGC), West Mifflin, Pennsylvania. The private pilot was not injured. Visual meteorological conditions prevailed and no flight plan was filed for the intended local personal flight that was to be conducted under the provisions of Title 14 Code of Federal Regulations Part 91.The pilot stated that on the morning of the accident, he called the fuel supplier and asked for the airplane to be topped-off, in preparation for a local flight. After performing a preflight inspection, he attempted to start the engine but it would not start. He tried three additional times, without success. On the fifth attempt, he followed the "starting engine when flooded" checklist. As the propeller was turning with the starter, he noticed white smoke "pouring out" of the engine cowl. He turned off the master switch and exited the airplane. He then opened the top engine cowling, and flames suddenly emanated from the left side of the engine, and the color of the smoke changed from white to dark black. He returned to the cockpit to retrieve a handheld fire extinguisher; however, the cockpit was filling up with heavy black smoke and he was forced to egress and unable to suppress the engine fire. The pilot added that there were no preaccident mechanical malfunctions with the airplane. According to Federal Aviation Administration and maintenance records, the airplane was manufactured in 1973. The airplane's most recent annual inspection was completed on September 8, 2015. At the time of the accident, the airplane had accumulated 6,336 total hours of flight time. Examination of the airplane by an FAA inspector revealed that the engine and compartment had incurred substantial fire and heat damage. Inside the cockpit, the fuel primer knob was found in the out/unlocked position. Additionally, review of a pilot's operating manual for the make and model airplane revealed: "…Engine Fire (During Start): Engine fires during start are usually the result of overpriming. The following procedure is designed to draw the excess fuel back into the induction system. a. If engine has not started: (1) Mixture – Idle Cut-Off (2) Throttle – Open (3) Turn engine with starter (This is an attempt to pull the fire into the engine.)…"