Crosman Trying To Re-Seal Crosman 140

I'm a newcomer here but need a bit of advise. I bought a Crosman 140 (I don't know what varient nor do I know how to tell) but it needs to be resealed. I cannto get the brass piece off of the pump rod I've cut down a washer and tried that to no avail. I've tried a screwdriver which was no benefit. I absolutely cannot get hat brass iece off and it is worth mentioning that based on plier marks on the aluminum parts of the air gun that it has been worked on before by someone who obviously didn't know what thtey were doing.
My only alternative at this point is to buy some Liquid Wrench and soak the end of the rod with the brass piece and see if that will loosen it or buy a replacement pump rod with a new pump cup installed. So my questions are:
(1) Anyone with otehr ideas to remove the brass peice holding on the pump cup and
(2) Is there a source where I might purchase a rebuilt 140 pump rod with the pump cup already installed?

Many thanks!
 
https://anotherairgunblog.blogspot.com/2008/10/getting-crosman-140-working-part-1.html?m=1

Looking at that one rod ( replacement ) is threaded on each end I guess for servicing it but the original rod he has below it not .

Then a guy in the comments brought it up as it's a press fit that may not be serviceable and he finding ways to keep his on the rod after it came off..

So I don't know .. looks like at one time if you needed a new rod seal you got the replacement threaded rod that can be took apart easy to reseal ?
 
Just as Airgun-Revisions stated, that ring is pressed on. I used a wiper arm 2 jaw puller to remove mine. I also applied a little heat to the ring with a micro torch before applying pressure with the tool. The 140 and 1400 series are really pretty easy to work on. The cup seal is the hardest part. Well, the quad seal in the exhaust cap can be a bugger to get out too. I sure love the crack/pop sound when firing!