What was found
APU FAILED TO START AFTER LANDING. FAULT LIGHT ILLUMINATED. ACFT GROUNDED. ACCOMPLISHED TECH SERVICE REQUEST. ALL CONNECTORS CHECKED OK. REPLACED BOTH START POWER UNIT AND START CONVERTER UNITS. ALL OPS NORMAL, GROUND VERIFICATION SATISFACTORY. IAW MM 49-41-71,49-41-61, WDM 49-62-12, 49-41-11, FIM 49-31/808. CHECKED FOR LOGGED FAULTS AND FOUND 3; APRIL 22, 2 TIMES, 49-31171 FCU FLOW DISAGREE, AND APRIL 18, 1 TIME, 49-41011, NO FLAME SHUTDOWN.