I recently built a new PC and when i try turning it on it will start up then turn it self off completly and nothing happens. I need help so please reply. Thanks.

Hello and weclome to PCHelpForum.

Firstly check your connections on ALL hardware,power connections.

Have you connected 24 pin or 20 pin or split 20/4 pin power supply to mainboard?

Have you connected the extra 4 pin power supply connection to mainboard in a seprate area on your mainboard.

Your mainboard should have 2 seprate ports for power supply connections.

Usaly a 20 or 24 pin power supply then a seprate 4 pin.

Could you post your computer hardware specs please

or 8 pin nowadays over the 4

the fact it starts and stops rules this out however as the pc would appear to run fans would spin etc just would not boot. I would guess faulty power supply but it could be a faulty motherboard. Have you connected the cpu fan to the correct header

Some have 8 pin like myne 4+4 but myne only uses the 4 pin.

still relevant as the system would still appear to be running just not posting if this was missing the op says it stitches on then off meaning it is something else

Yes it is a 20 pin and 4 pin and i have connected it together so none of them are in the wrong place. Does this mean i will have to get another power supply or motherboard?

Do you have another power supply to test the system?