What was found
AFTER ENGINE START, CAPT'S AIRSPEED AND ALTITUDE INDICATIONS WERE BLANK. CAPT'S & F/O'S FD'S WERE ALSO BLANK. AIRCRAFT BACK TO BLOCK AND GROUNDED BY MAINTENANCE. NO EICAS OR STATUS MESSAGES DISCREPANCY STARTED AFTER GPU POWER TRANSFER. GPU HAS AN ELECTRICAL SURGE, CHANGED GPU, PERFORMED RIGHT ENGINE START AT THE GATE AND POWER TRANSFER WAS SUCCESSFUL. OPS CHECK SATISFACTORY AT THIS TIME. A/C REMAINS NO ETOPS.AC RETURNED TO SERVICE.