MECHANIC SIGNING FOR MAINT WORK DONE ON AN MD-80 ACFT FOR A LEFT ENG START VALVE PROBLEM; IS INFORMED APPROX ELEVEN MONTHS LATER HE SHOULD HAVE STATED HE REINSTALLED; NOT REPLACED; THE START VALVE AIR FILTER.

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ON JUL/XA/08; I WAS CONTACTED BY OUR UNION REPRESENTATIVE REGARDING MAINT WORK THAT WAS DONE BY ME THE NIGHT OF SEP/07 IN ZZZ. IT INVOLVED AN MD80 ACFT THAT HAS THE L ENG START VALVE ON MEL. AS FAR AS I CAN RECALL; IT WAS PLACARDED BECAUSE THE START VALVE WOULDN'T OPEN. PREVIOUS MAINT DONE TO IT WAS REPLACING THE START VALVE A COUPLE OF TIMES WITH NO HELP. THE SECOND TIME THE VALVE WAS REPLACED; THEY INDICATED THAT THE AIR FILTER FOR THE START VALVE WAS NOT ALLOWING AIR FLOW TO THE VALVE. THE INFO ALSO PROVIDED FOR THE PART NUMBER FOR THIS FILTER. WHEN I LEARNED THAT THE AIR FILTER WAS NOT IN STOCK AT THAT TIME IN ZZZ; I WENT AHEAD AND REMOVED THE AIR FILTER FROM ITS HOUSING AND PERFORMED A VISUAL INSPECTION FOR ANY SIGN OF DEBRIS BUILDUP OR CLOGGING. WHEN I DID NOT FIND ANY DISCREPANCY ON THE FILTER; I BLEW ON THE FILTER TO VERIFY THAT AIR PASSES THROUGH IT; AND IT DID. SO I REINSTALLED THE FILTER ELEMENT. THEN AS PART OF THE TROUBLESHOOTING THAT ME AND A FELLOW MECH DID; WE WENT AND REPLACED THE 8TH STAGE CHK VALVE BEING SUSPECT THAT IT MIGHT BE BLEEDING SOME AIR OUT CAUSING LOW PRESSURE TO THE START VALVE. THEN WE PROCEEDED WITH THE OPS CHK. WE TURNED ON THE APU BLEED AIR SWITCH AND AFTER WE GOT DUCT PRESSURE; I MOVED THE L ENG START SWITCH TO START POS. THERE WAS NO MOVEMENT ON THE START VALVE. THEN I RELEASED THE START SWITCH AND MOVED IT BACK TO START POS THE SECOND TIME AND THIS TIME THE VALVE OPENED AND ENG STARTED TURNING UNTIL IT REACHED MAX STARTING ROTATION. REPEATED THIS SEQUENCE A COUPLE OF TIMES; AND VALVE OPENED AND CLOSED NORMALLY. BUT THE TIME WHEN WE SWITCHED OFF THE APU BLEED AIR AND DECIDED TO DO THE TEST AGAIN; AFTER TURNING THE APU BLEED AIR TO 'ON' AND DUCT PRESSURE ESTABLISHED; THE FIRST TRY WHEN WE MOVED THE STARTER SWITCH TO START POS; THE VALVE FAILED TO MOVE AGAIN BUT ON THE SECOND AND FOLLOWING ATTEMPTS; THE VALVE OPENED AND CLOSED. AFTER THESE TESTS WERE DONE WE DECIDED THAT THERE HAS TO BE OTHER FACTORS CAUSING THE START VALVE NOT TO OPERATE NORMALLY; SO WE LEFT THE SYS ON PLACARD AND WROTE ON INFO THAT IT NEEDED FURTHER TROUBLESHOOTING. AS FAR AS MY INFO SIGNOFF WAS CONCERNED; I WROTE THAT I REMOVED AND REPLACED 8TH STAGE CHK VALVE AND AIR FILTER. I WOULD LIKE TO CLARIFY THAT WITH REGARDS TO THE AIR FILTER; IT WAS REINSTALLED AND NOT REPLACED. I ALSO INCLUDED THE RESULT OF OUR TROUBLESHOOTING FOR THAT NIGHT. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: REPORTER STATED THE SAME ENGINE RECENTLY HAD A FIRE WARNING ALARM GO ON AFTER TAKEOFF AND DURING THE FOLLOWING INVESTIGATION OF PREVIOUS MAINT PAPERWORK SIGNOFFS; QUESTIONS AROSE WHETHER HE ACTUALLY HAD REPLACED; OR; CLEANED AND REINSTALLED THE MD-80 LEFT ENG STARTER AIR FILTER.