AN MD80 DPTED DEPRESSURIZED WITH THE CABIN ALT CONTROL LEVER NOT COMPLETELY LOCKED UP AFTER THE CAPT TOUCHED BUT DID NOT MOVE THE LEVER DURING PREFLT.

Narrative

DURING THE PERFORMANCE OF THE BEFORE STARTING ENGS CHKLIST; THE FO READ 'PRESSURIZATION;' AND I RESPONDED; 'AUTO (UP) AND SET.' I SIMULTANEOUSLY TOUCHED THE CABIN ALT CTL LEVER WITH MY R HAND AND CONFIRMED THAT IT WAS UP. SUBSEQUENT EVENTS PROCEEDED NORMALLY UNTIL THE CLBOUT. OUR DEP FROM ZZZ WAS FROM RWY XXL AND WAS RWY HDG TO 10000 FT. AFTER REACHING 8000 FT WE WERE CLRED TO 16000 FT. UPON READING 10000 FT (AND STILL CLBING); WE RECEIVED BOTH AURAL AND VISUAL INDICATIONS THAT THE CABIN ALT HAD EXCEEDED 10000 FT. WE STOPPED OUR CLB AT 10400 FT AND REQUESTED A RETURN TO 10000 FT; WHICH WAS GRANTED BY ZZZ DEP. ASSESSING THE SITUATION WE DETERMINED THAT THE CABIN ALT CTL LEVER WAS PROBABLY NOT IN THE DETENT (EVEN THOUGH IT WAS STILL UP). I PHYSICALLY MOVED THE LEVER AS FAR UP AS IT WOULD GO TO MAKE SURE IT WAS IN THE AUTO POS. TO ASSIST THE ACFT IN REACHING A LOWER CABIN ALT; WE REQUESTED AND RECEIVED A CLRNC TO 8000 FT. ZZZ DEP ALSO GAVE US WHAT AMOUNTED TO A L 360 DEG TURN WHILE WE TROUBLESHOT THE SYS. AFTER A FEW MINS; THE CABIN PRESSURE WAS UNDER CTL AND WE PROCEEDED TO ZZZ1 WITHOUT INCIDENT. IN RETROSPECT; IT MIGHT HAVE BEEN BETTER DURING THE PREFLT TO PHYSICALLY MOVE THE LEVER UP AS FAR AS IT WILL GO; RATHER THAN JUST TOUCH IT AND VISUALLY CONFIRM THAT IT WAS UP. THIS WAS THE FIRST TIME THAT THIS HAS EVER HAPPENED TO ME; AND FROM THE LESSONS LEARNED; I WILL MAKE SURE THAT IT DOESN'T HAPPEN AGAIN. SUPPLEMENTAL INFO FROM ACN 792538: SUM: FO BELIEVES NUMEROUS DISTRS DURING THE PRE-BOARDING AND DESIRE TO COOL ACFT FOR PAX COMFORT RUSHED CREW DECISIONS AND FO SHOULD HAVE BEEN MORE VOCAL IN SLOWING THINGS DOWN DURING THE PREFLT PHASE. CREW DID WORK WELL TOGETHER IN THE FLT PHASE TO ENSURE THAT THE ACTIONS TAKEN WERE SAFE AND DID NOT VIOLATE FAA/COMPANY PROC. THIS WAS A GOOD LESSON LEARNED; TO ALWAYS ENSURE THAT CTLR LEVER IS IN THE DETENT AND TO REMEMBER TO BOTH AURALLY AND VISUALLY CONFIRM ALL CHKLIST ITEMS IN THE COCKPIT.