Question GPU Red flash

[Keplerm13]

I am currently in the process of case swapping. I only have my gpu, mobo, and cpu plugged in with power. I wanted to test to see if it would boot. When I turned on the computer the gpu just flashes red for a second and then stops. I unplugged my gpu power cables and this still happened. I checked all cables to make sure they are plugged in all the way and this still happened. Nothing is lighting up in my computer besides this red flash on my gpu. My psu fans are also not spinning when i power on. I have even tried plugging one of my case fans in and that does not work either. Plz help
EDIT: I have a evga 1080. A Gigabyte Z370P D3. Intel i5 8700k. 16gb of corsair vengeance pro ram at 3600 mhz. And a 650w bronze evga power supply

 

[Lutfij]

How old is the PSU in question and what series is it from? You might want to breadboard the system with the bare essentials. Since you have an iGPU on the processor, try powering up without a discrete GPU in the build.

 

[Keplerm13]

I have already tried this and the psu is not the problem because i have tried multiple psus. One of them is mine which was working in my old case and the other was my friends psu that works in his current build