On September 27, 1993, at approximately 1510 central daylight time, a Beech A36, N80010, was destroyed by fire during engine start at the Hobby Airport, in Houston, Texas. The airplane, being flown by an ATP rated pilot, was about to depart on a local flight. There was no flight plan filed and visual meteorological conditions prevailed throughout the area. Neither the pilot nor the passenger were injured. According to the pilot, who was a Beech sales person, the flight was to be an acceptance flight prior to sale to the passenger. The pilot stated that he utilized the high boost pump to pressurize the system and then started the engine. The engine started and then quit. He applied boost pump again and restarted. During the second start, the pilot noted flames coming up from the engine compartment toward the cockpit door window. The pilot and the passenger immediately exited the airplane prior to its being engulfed in flames. The pilot failed to return the Pilot/Operator Accident Report that was provided to him following the accident. Investigation revealed a cross threaded output line on the engine driven fuel pump which allowed fuel to leak into the engine compartment. The fuel pump had been removed earlier in the day for compliance with a service bulletin and re-installed. Following the completion of the maintenance, the airplane was run up by the lead mechanic who stated that he also performed a post- run inspection. He later stated to his supervisor that during the run up he had to keep the electric boost pump operating in the low position to prevent the engine from running rough. However, he did not relate the situation until after the mishap.