Power button does not work.

My sons MBP 15, sustained a coffe spill. Power button did not work. I cleaned logic board and case. was able to start computer only after connecting to the DC power adapter. Everything works - hard drive, display, DVD, all keys -except the power button. Power button will not shut down computer. I can restart and shut down through OS. If I shut down I have to open case, disconnect battery for a few seconds, reconnect DC adapter, and computer will restart. I looked at button inside case and it seems to work mechanically. Can anyone please help me? Should I try to disassemble and clean entire keyboard? Is this a logic board problem?