What was found
ACARS MESSAGE, FLT 745 INDICATE COLD SOAK START FAIL FL 360, 310 MEL FAULT. ACFT GROUNDED. FOUND FAULT 49-31171, FUEL CONTROL UNIT FLOW DISAGREES WITH COMMAND. REPLACED FCU WITH NEW. ALL OPS & BITE CHECKS GOOD, IAW AMM 49-31-11. CSS ATTEMPT AT FL360, FAULT LIGHT ILLUMINATED SECOND CSS ATTEMPT AT FL 330 APU STARTED, BLUE APU GEN OFF LIGHT ILLUMINATED GOOD-NORMAL FREQS AND VOLTS. ACCOMPLISHED BITE CHECK ON APU, GROUND, OPS CHECK OF APU NORMAL. REMAINS ON 49-99A.