Apparently, filling that hole can damage the check valve. Popatachi goes into more detail on how this happens in his 3k check valve repair guide. Basically, the check valve uses a rubber sealer, part of which extends into the hole when the pump is at rest. Fill the hole, & you risk dislocating the rubber sealer, rendering the check valve, & the rest of the blaster, useless. (unless you know how to repair the valve, like Popatatchi) Obviously, I didn't want to break my blaster, so I made this guide.
So the first order of business is to open the blaster. Once this is done, take a look at your pump shaft.
See that pin near the base of the pump head? Remove it, as this lets you remove the pump head, which is what you'll be working with. (I am aware that that photo is on the blurry side, but I couldn't help it; my camera is cheap.)
Now cut the top off, just past the side hole.
Watch out for the second layer of plastic; the two halves of the pump head are glued together, which is why you have to cut the top off in the first place.
A spring & a black rubbery thing (I don't know what it's called) will come out. You won't need the spring, just the black rubbery thing.
Put the black rubbery thing back in...
... and fill the cavity with hot glue.
Before the glue dries, carefully put the two halves of the pump head back together. Run a ring of hot glue around the cut to ensure a more solid connection.
Wrap some e-tape around the cut area to further solidify the connection; there's probably better stuff to do this with, but e-tape's all I had.
Now reattach your pump head to your pump shaft, put the pin back in, & there you have it, a plugged pump that won't damage your check valve. The hot glue should hold up reasonably well; I've pumped the blaster up five times & still haven't had any problems with the oprv. I'll pump it up more times when the rest of my 2k is modded the way I want it, & see how the glue holds up to that. Until then, I'm open to any comments or suggestions that you might have.
Edited by F1Nerf, 03 June 2014 - 10:55 PM.