Before you power anything up I would jumpstart your PSU and only plug in the pump. Leave it like that for at least a couple of hours and put some paper towel down under your components, you can then inspect the paper towel for any dampness. If you have UV coolant you can also see little leaks with your UV light powered.
Anyway, don't power anything untill after a good leak test. I wish I had followed that advise at first. I didn't and got a couple of drops in my PSU...two week later I was finally up and running when my new PSU got here
I actually use a separate 12V power supply to do mine, but if you don't have it, you can bridge the green and a black wire on your 24 pin to power up the PSU and then just plug in your pump.
Here is the jumpstart instructions:
As tempting as it is...don't rush it..speaking from painful experience here..