Computer wont boot with 8 pin power plugged in

[velosteraptor]

I finished installing a new water cooling system today, and everything went well on my test bench. When i brought the computer to my desk and hooked it up, it booted as normal for a few minutes, and then shut off. I determined that the cpu was getting too hot, and would shut off. While trying to troubleshoot it, one time the PC would not turn on. When pressing the power button, the LEDS and fans spin/flash for about half a second, then go dark. Through various troubleshooting, ive determined that the machine will only boot if the 8 pin connecter to the motherboard is unplugged.

Through spare parts, i have ruled out my RAM and video cards

Im assuming its either my MOBO or CPU.. is there any way to tell specifically?

Help would be great, Thanks.


System Specs:

MSI 890FXA-GD65
AMD 1100T
Radeon 5770 and Radeon 6770 in crossfire
8GB (4 sticks of 2GB each) RAM
1 Seagate 750GB hd
XSPC rasa 750 RX240 watercooling system
NZXT Phantom
850 watt Thermaltake Modular PSU

 

[sephmeister]

I'm not sure that entirely rules out PSU either... try reseating your processor as well as ALL power connectors on your motherboard.

Also, if everything went smoothly on the bench it suggests your case is likely shorting it out, double check your mounting screws and all USB/front panel connectors as this could be a problem as well.

 

[TenPc]

8GB (4 sticks of 2GB each) RAM
Can you be more specific? Brand name? speed?

Does it comply with the motherboard specs?
Supports four unbuffered DIMM of 1.5 Volt DDR3 800/1066/1333/1600*/1800*/2133* (OC) DRAM, 32GB Max


If the cooling CPU system is not touching the cpu (with Thermal paste in between, of course) then it is not doing its assigned job of dissipating the heat.

Check the temps in BIOS PC HEALTH.