What was found
ON FLIGHT 4766, AT THE GATE WITH ENGINES OFF, EXTERNAL AIR REMOVED, AND ON GROUND POWER ONLY, COCKPIT AND CABIN FILLED WITH ODOR OF SMOKE. THE ACFT WAS REMOVED FROM SERVICE. NO SMOKE NOTED IN LAVATORY, GALLEY, CABIN, COCKPIT, ANY CARGO AREA. CONFIGURED ACFT WITH ALL AVIONICS ON AND ONLY GPU POWER ON FOR OVER AN HOUR. AT NO TIME WAS THERE ANY UNUSUAL ODOR. THE ACFT WAS RETURNED TO SERVICE.