A B767-300ER HAD CHRONIC GND APU START PROBS WHICH ALWAYS GND CHKED OK. TECHNICIANS FOUND CREW START PROC DIFFERENT FROM TECHNICIANS START PROC IN RUNUP HANDBOOK.

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ACR ACFT XYZ HAS HAD A HISTORY SINCE AT LEAST MAR/00 OF THE FLC'S NOT BEING ABLE TO START THE APU. NUMEROUS TIMES MAINT CHKED THE ECU WITH NO FAULTS FOUND; AND THEN ACCOMPLISHED A NORMAL START. ON APR/MON/00 I LOOKED AT THE APU FOR A NO START LOG ITEM. THE ECU HAD NO FAULTS AND I ACCOMPLISHED SEVERAL NORMAL STARTS; SO THE ITEM WAS CLRED. ON APR/THU/00 THE ACFT AGAIN CAME TO ZZZ WITH APU START PROBS. I ATTEMPTED AN APU START AND THE APU STARTED NORMALLY WITH NO FAULTS. IN INTERVIEWING THE CREW; I FOUND THAT FLCS USE A DIFFERENT PROC FOR STARTING THE APU. FOR THE FLT MANUAL; THE CREWS ROTATE THE START SWITCH TO ON; WAIT FOR THE FAULT LIGHT TO FLASH; THEN ROTATE TO START POS AND RELEASE. PER THE HANDBOOK WHICH THE MECHS USE; THE START SWITCH IS ROTATED DIRECTLY TO THE START POS THEN RELEASED. I THEN ATTEMPTED AN APU START USING THE PLT'S METHOD AND WAS ABLE TO DUPLICATE THE FAULT. I THEN DEFERRED THE APU AS USABLE AND DESCRIBED THE METHOD OF STARTING THE APU AS CALLED FOR IN THE HANDBOOK. THE APU HAS CONSISTENTLY STARTED WHEN USING THE HANDBOOK METHOD; AND SINCE THERE IS NO MEL ADDRESSING THIS; I DEFERRED THE APU WITH NO REF. THE REASON I MADE A DEFERRAL IS I FELT THE START SYS SHOULD BE LOOKED INTO FURTHER EVEN THOUGH THE APU STARTED USING THE HANDBOOK AND THE HANDBOOK TAKES PRECEDENCE OVER THE FLT MANUAL.