My computer shuts down immediately after I press power button.

[Ryan81198]

So I just built a new computer (my first one) I don't really know much but it was working fine then went downhill. When I press the power button the fans spin and light up then immediately turn off. I've tried tons of things, I've installed 2 new MOBO's 2 new CPU's I've gotten numerous new RAM, a new power supply but still does that on off thing instantly. How can I fix this?
Any help would be much appreciated! Thank you in advance!

 

[Colif]

what are the parts in the PC?

have you tried to boot up with no graphics card & 1 stick of ram? see if it works off the integrated graphics

 

[Rhinofart]

Have you tried booting it all up outside of the case? Maybe you have a grounding problem with the components in the case.