You proved there is some failure on the motherboard and what's on that board as a final test try a power up with just the board and the PSU. No CPU, memory, HDD, ODD required.
About a week ago I spilled some koolaid on my computer (I built this computer about 8 months ago with 0 problems on my first build . It didn't look like much got on my computer, but being safe I unplugged everything and waited for it to dry/wipe it up before turning it back on. When I turned it back on it was on for about 2-3 seconds then shut down. Ever since then it has not started up. I will get a single click noise from the PSU every once in a while, when pressing the power button. I have tried switching out the PSU and that does not change anything. I actually purchased a brand new one, originally thinking my psu went bad, and same result... However, if I unplug the 4 pin CPU power cord, all of the fans and power supply and everything gets moving and going, its just a black screen because no cpu power.Now I'm thinking it could be a bad connection on the mobo? Im not that tech savvy so be easy with me guys. Thanks!