What was found
(CAN) NR 2 ENG STARTED NORMALLY, DURING NR 1 START, EXPERIENCED A ENG HOT ICON WITH FADEC ABORT OF START. LOST AC ELECTRICAL POWER. NR 2 ENG & APU SHUTDOWN. ACFT TOWED BACK TO GATE. ACFT POWER SHUTDOWN. CREW REPORTED SYNOPTIC PAGE INDICATED AC BUSS 1 FAULTED. CB-N2 POPPED. F/A OBSERVED A FAINT ELECTRICAL ODOR IN CABIN, SAME ODOR EVIDENT IN COCKPIT. NR 2 CIRCUIT BREAKER RESET WITH EXT AC POWER. APU & NR 2 ENG STARTED. ANOTHER START ATTEMPT MADE ON NR 1 ENG. JUST PRIOR TO THE STARTER CUT OUT OF THE NR 1 ENG, L COWL A/I DUCT CAUTION MESSAGE BECAME EVIDENT. AT THE SAME TIME, STRONG ELECTRICAL ODOR . ENGINES SHUTDOWN & POWER REMOVED FROM THE ACFT. 3 POPPED CIRCUIT BREAKERS ON CPB2. FOUND EVIDENCE OF HIGH TEMP. ON CB`S & ASSOCIATED BUSS BAR DISCOLORED. NO DAMAGE NOTED TO WIRING OR ATTACHMENT LUGS, THE N3 CIRCUIT BREAKER SCREW FOUND LOOSE AT CB-N3 & BUSS BAR (NR250 AND NR255) INTERFACE.