New build boot loop?

[Fornever]

I have just finished my first watercooled build and am trying to start the machine. When I flick the PSU switch and touch the Power button, the system will start, run for about 5-10 seconds, shut off for about 5 more seconds and repeat. The last number on my mobo's LED indicator is 62 when the ROM switch is flicked one way, and b2 for when it's flicked the other way.

The DVD drive and the hard drives seem to be working, my pump / resevoir unit is running and my fans are working as well, but I am not getting any signal from my monitor - I've tried both VGA and HDMI to no avail.

I've tried disconnecting all drives - CD and hard disks - and removing one of my Kingston Fury DDR4 4GB RAM sticks. Still nothing. I also have a GTX 1080 with a waterblock on it sitting in its slot, but I didn't connect it to my PSU yet since I just want to get things running.

So what do I do? I cannot reach the BIOS so I'm at a real standstill here.


Specs:

Mobo: Biostar Z1​70GT7
CPU: Intel i5-6770k
PSU: Corsair RMx 750W 80+ Gold
RAM: Kingston Fury DDR4
Drives: 1x 128GB SSD, 1x 2TB HDD, 1x CD/DVD writer, 1x fan controller
Watercooling: Thermaltake PR22 pump / resevoir, EK Supremacy EVO CPU waterblock

 

[Fornever]

Found the problem, for some reason the machine refused to boot properly unless the GPU was powered via the PSU with the PCI-E cable, which I avoided doing in order to try and leak test the loop. Oh well.