GPU Shutdown Problem

I have an Alienware X51 bought a year ago. It came with GTX 645 and a 240W external brick. I found out that you can run a gpu with a psu dedicated only to it.
So, I bought a Zotac Nvidia GTX 760(reference) and a Corsair VS450. I connected the ON wire(Green) on the mobo clip to the ground wire(black) on the same clip. i fixed up the rest of the pc and ran it. It worked perfectly for a week. Now, when i run games like Titanfall(within 15 mins of playing), Lego Marvel Super Heroes(within 45-50 mins of playing), the screen goes blank and a fan in my case goes crazy fast. all this happens while my pc is still on(all lights on), and my psu fan is still running.(Sometimes it simply reboots)
But this problem doesnt occur while playing NFS Rivals on MAX, Splinter cell Blacklist on MAX, or while running 3DMark Vantage benchmark.I have the latest drivers installed and my BIOS is A12.
I tried FurMark GPU stress test. At 99% load, and GPU temp maxing out at 85C, nothing crashed for 20 mins or so....so i dont think its the gpu. Its only happening with games.
I also tried Intel burn test on standard stress(10 times) and on high stress(10 times). the CPU temps never exceeded 62C, and there was no crash or anything abnormal. I also ran the standard windows memory check which booted my pc into kind of a safe mode and checked both the memory modules with no errors. I really cant seem to figure out the problem.
I've noticed that the problem occurs around the time when the textures are trying to load.

Specs:
CPU: i5 3330
Ram: Hynix 8GB (4GBx2)
MOBO: Alienware 0KM92T

Please Help

 

I don't recommend using external PSU for video card unless PSU is designed for that use. There are (was) some PSU's that only had couple of PCI Express connectors.

I cannot undestand why you don't just put that 450W PSU to whole system? Much safer and more reliable solution.

Reason for problem? I guess that VS450 PSU don't like load on +12V only.

 

The PC's power supply is stock and is a bit complicated inside(Eg. the power for the lighting, hubs, drives,etc.).

If the cause of problem is my VS450 PSU, then how come it doesnt occur when running FurMark which puts my GPU on 99% load, which i ran for 20 mins straight without a hitch? (as i mentioned above)

 

450 watts for GTX 760 is not problem. Problem is that if you don't have any load on +5V and +3.3V rails, that may cause problems. In that case, changing load (and also low load) may be worse than keeping it on same level (Furmark).

 

So will it be enough if i connect the P1 connector to the mobo and leave the rest as it is?

 

P1 connector is what? Molex connector to motherboard?

Perhaps it's enough to plug molex connector from Corsair to HDD and DVD drive.

 

THANK YOU SO MUCH!!!! First I tried temporarily(with case open cuz cable isnt long enough to snake inside the case) connecting the P1 connector(ATX 24 pin) to the mobo as it has both the 5v and the 3.3v. worked like a charm....then i thought, why not connect a sata to the psu as even that has a 5v and 3.3v, tried that and even that worked like a charm.....now(after abt 2 hours of scavenging for the right connectors and after 1-2 hours of work), it works perfectly. I just checked your post after finishing up and even you suggested the same...guess we think alike(at least when it comes to problem solving, kinda ).

Once again, THANK YOU....didnt think that the psu i bought would be that shitty

 

Good that your setup works.

 

It worked fine for a few days with the hdd also connected to the corsair(so, gpu and hdd only connected), but its happening again now. when I reboot(or force reboot) after the crash it says HDD not detected even though I can feel it run as its still vibrating(i have my hdd outside my case in a protective cover to improve circulation inside my rig). Im having to switch my Corsair main off then back on for it to work.
But it happens after playing for like 5-10mins(unlike earlier, when it would happen when its loading) and doesnt happen on full load(Furmark), only while playing games. Also, it happened once when i minimised Furmark, doesnt happen when i close it. Could it be a faulty PSU?I think it is. If yes, then my dealer has a 30 day replacement guarantee which ends on 14 of this month and i will get it exchanged....

 

There may be problem with something else than PSU. Motherboard and video card are main suspects in cases like this.

 

everything is fine if i put my old gpu back. i feel that the psu stops supplying power for a moment or so causing the problem. Im supposed to switch my corsair on then the pc. Once i had forgotten to switch my corsair on and i switched my pc on, it made the same kind of noise it makes when it hangs(same fan inside case goes crazy fast).

 

Maybe some more load on PSU without motherboard could help? Now you have quite little.

 

another hdd? ill try that.....

 

But I don't get one thing, why does it work perfectly for the first 3-4 days(no matter how much I play), then start showing problems? First time when I upgraded, I played without problems for 4 days, then bam. After I fixed it by connecting HDD, I played a lot(finished watch dogs in 3 days), then it started troubling again. So now, IF I try to fix by adding another HDD, and its starts showing issues after 3-4 days, I won't have a chance to request a replacement/refund from the seller and instead will have to ask the manufacturer, which won't be simple as I live in India.
Thank you once again for helping me, no one has been able to help me or even tried. I posted in a couple of other places like tomshardware and nobody helped. I really appreciate it.

 

Those kind on random usually are based on leaked condensators. They (may) work fine, then suddenly crash. So check motherboard for leaked condensators first. Also check video card, most probably problem is not there however. Also PSU has condensators, but do not open it. It's dangerous.

Also, 4 memory sticks is not recommended. Try what happens with 2 sticks or even 1.

And still something, you can try to add any type of load to PSU to provide more load. Lamp, resistor, fans etc. Perhaps PSU connected to video card only is not too pleased for switching between minimal and little load.

Of course, problem may lie in video card, then only solution is to change it.

 

I checked all the capacitors, they are all in top condition. I only have 2 memory sticks(each 4GB), as i said in my 1st post.

I read somewhere that ATX based PSUs need atleast 10W of load on 5V to function properly on 12V(as you said), my HDD was apparently only 7.5W. So, i bought more sata cables and now i have a total of 3 HDDs connected(i figured i could use the extra space). I havent tested yet as I dont have enough time to do so, will test as soon as possible and report.

 

Played three hours straight.Worked fine. Hope it stays that way. Thank you for all your help.