PC won't getting no signal with graphics card output

[JakeF]

Right so I've had this problem for months now, when I connect my cable into my onboard graphics I get a display and get right into windows but if I try to use my gpu my monitor says no signal,

Things I've tried:
Another gpu and I got the same problem
Different cable
Changing the bios to pci slot
I've sent my psu and motherboard back and got new ones and the problem still consists..

I'm really stuck on what the problem is now

 

[QwerkyPengwen]

when installing a GPU into a system that I'm assuming didn't have that type of GPU or it's brand in the system before (i.e. you currently have something like a GTX 970 in but in the past you had an older nVidia GPU) then the onboard graphics are the only thing that's going to work at first. Download and install the necessary graphics drivers for the GPU before attempting to use it as the primary display driver. Also, what kind of GPU is it? does it require you to plug in external power cables from the PSU? If so do you have them plugged in?

Can you give us a list of the hardware in your PC.
i.e. - mobo, gpu, psu, and their brand/model

 

[Phillip Corcoran]

"Changing the bios to pci slot"

If the graphics card is in a PCI Express slot then you need to set graphics in BIOS to PCI Express, not PCI.

Also, as previous poster says, if the graphics card needs 6-pin or 8-pin auxiliary power then you need to make sure the appropriate power cable(s) is/are connected to it.