What was found
PDX FLIGHT NR 2169, AFTER ENGINE STARTS WITH BLEEDS BOTH ON STRONG BURNING ODOR NOTED ON FLIGHT DECK AND IN THE CABIN. AFTER BLEEDS SELECTED OFF THE ODOR DISSIPATED SLIGHTLY. IN THE CABIN THE ODOR WAS STRONGEST IN THE AFT. MAINTENANCE COMPLIED WITH FAULT ISOLATION FIGURE 119 OF PWC MM 72-00-01. NO DEFECTS NOTED. STARTED BOTH ENGINES NUMEROUS TIMES SELECTING BLEEDS ON ONE AT A TIME AND TOGETHER NO BURNING ODOR OR SMOKE NOTED IN FLIGHT DECK OR CABIN. NO PARTS REPLACED. AIRCRAFT RETURNED TO SERVICE.