Windows 7: New PSU, PC won't turn on

My sister just got a new PSU for her PC, I put it in, when on the motherboard has a slow blinking green light and nothing else, the CPU's fan doesn't even rev or anything.

PSU is a Corsair VS550, motherboard is an ASUS H81-PLUS. There is one different compared to the previous PSU though which I don't know if it's an issue or not? The CPU plug on the motherboard if a 4 pin labeled as EPU, whereas this new PSU only has an 8 pin CPU plug.

I know it's just two of the four pins connected together, but just mentioning it in case it's relevant.

Does the PSU have a single 4 pin plug at all? If not you may need that.

You could try the other side of the PSU's 8 pin connector.

Did you plug in the 24 pin MOBO connector?

I agree with Simpilot that it's probably a connection issue. The last Corsair PSU I bought the box it came in had what each of the connecting cables is for.

No there doesn't seem to be a 4-pin one at all, I tried both sides of the 8-pin with the same results, and yes I had the big motherboard one connected too.

Going to look into one with a 4-pin connector, there's a lot with 8-pins it would seem...

Detach the four-pin connector from the 8-pin cable, and then plug that four-pin cable directly into the motherboard ATX12V.

Just realised that could happen, tried it, same thing. Just the blinking green light.

The ASUS H81-PLUS requires a PSU that complies with ATX 12V specification 2.0 (or later). The VS550 complies with that.

I would check your connectors again, or put the old power supply back in and see if that works.

This YouTube video might help you with those connectors.

Corsair VS550 power supply review, unboxing how many connectors, cables and stress test - YouTube

I'm having the same problem and will test the PSU next. I left the PC to update and proceed on installing the new brake kit and fuel wheels on the truck. When I return back the PC is off and can't power on so I changed up the extra Corsair PSU. Gonna try those tests and see if the PSU will work.