B737-800
Flight Crew Air Transport Pilot (ATP)
Other / Unknown
Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Maintenance; Deviation / Discrepancy - Procedural Published Material / Policy
General Maintenance Action
Equipment / Tooling; Procedure
During our preflight check we discovered that when the Captain or First Officer mask was tested the crew oxygen pressure went to zero. The crew oxygen bottle had been replaced the night before.  Maintenance was called and the crew oxygen valve was discovered to be not fully open. Maintenance opened the valve fully; safety wired it; and signed it off in the logbook.
[Report contains no additional information].
A B737-800 Captain and First Officer discovered their oxygen mask pressures at 0 PSI during the preflight mask test and maintenance discovered the oxygen bottle valve not fully open after the bottle had been replaced the previous night.