computer shuts off with no display

when i turn my computer on it will turn on but i wont have any display then after being on for 5 seconds everything will turn off and then wait about 3 seconds and will comeback up with no display it worked fine before i took my fan/heatsink out but i wouldn't see why that would cause this i have also taken out my bridge video cards and placed them back in i removed the ramm to see if that would cause it too and i still have the same problem i dont know how to get the display to come back and it wont even beep

 

Did you reconnect the fan for the heatsink? It might be a safety cut out due to no fan being detected.

Does your motherboard have onboard video? If so then try using that.