What was found
ON FLIGHT 3633, DURING FLIGHT HEARD THUMP UNDER FLOOR, "FUEL 2 LO LEVEL" ON EICAS, NR 1 FUEL QUANTITY TO DASHES. MULTIPLE WARNINGS IN COCKPIT. ELECTRIC OR SULPHUR ODOR NOTED IN CABIN AFTER LANDING. AIRCRAFT REMOVED FROM SERVICE. REMOVED AND REPLACED NR 1 ESSENTIAL BUSS CONTACTOR OPERATIONAL CHECK GOOD IAW AMM 24-60-03. AIRCRAFT RETURNED TO SERVICE.