HP Z640 won't turn on after graphics card upgrade

[Oldnewb]

Hello,I risked upgrading my graphics card and after carefully searching I unplugged my computer,pressed the start button to drain,removed  my old nvidia 310 card, put in the  nvidia Quadro 5000 (which shows its compatible via HP's website),plugged in the HDMI cable,plugged the power cord back in,pressed the start button,it powered up and got the on screen message that the new card needed power to function. Searched again for where the 6 pin power would be and the utube vid showed that the power cable's are "connected" to the fan housing,just for shipping until needed.I disconnected the cable marked G1,plugged it into the card,a green light came on,I pressed the start button and the white light come's on but won't start.No beeps or error code flashing lights.I searched for a solution and removed/re-installed the ram and battery,removed the new card and replaced the old card,unplugged the PCU and a few other cable's with no luck. My computer: HP Z640,32G ram,8 core,2.5ghz  .Thank you all for any help. Suuuuuuuper bummed.

[Davidxhite]

Dealing with the same issue.  Installed new graphics card and getting no boot.  Just white led.
Tried clearing cmos.  No joy.  Put old card back in, no joy.  What is going on? 

[Oldnewb]

Sorry to hear that. I researched this computer before I bought it and thought it was solid. Good luck!