Here is what I did to repair the manual oil pump, I didn't take any pics of the process, but can probably explain it well enough.
After pulling the tank and disassembling the rod, the only thing left was the pump body.
@heimannm wasn't kidding when he said it was tricky to get out and back in, but it's easy to get the hang of, once done a few times. (which you may have to do)
After inspecting and cleaning the oiler rod, return spring and pump body, I could find no sign of any binding but could still see/feel it when using the manual oiler. Thank you Mark for pointing out to my stupid-*** the possibility of a kink somewhere in the pump itself.
After reading that and thinking on it, I figured the the best thing was to smooth out any anomaly in the pump body, so I used sandpaper and the oiler rod as a kind of cylinder hone to knock-down any binding points and smooth the walls of the pump body.
This is what I used: Penetrating oil as a lube (liquid wrench), the oiler rod as a hone, a toothpick and some very fine sandpaper (2000 Grit). After cutting small strips of the 2000 grit to size, I wrapped a strip on the end of the oiler rod, sprayed some lube on the pump and rod, then started twisting/turning downwards slowly until reaching the bottom of the pump body. However, the paper would ride up and couldn't reach the very bottom of the pump body. (where the most friction was felt) So I rolled a piece of sandpaper and put it inside the pump body using a toothpick, then the rod to push it down to the bottom than repeated the downwards turning/twisting motion.
I would frequently stop to reassemble the oiler assembly on the bench to check the fit of the rod until very little binding was felt in the pump, making sure it isn't loose in the pump body and if there was any minimal binding, the return spring would be able to overcome it now. After a final cleaning of the pump and reassembly, it's oiling properly, the rod is not loose in the body, it actuates smoothly and does not stick or bind any more. The whole thing only took 20-30 minutes, as compared to waiting 4-7 days on a replacement pump. I expect the "repair" to last for a long time, especially with bar oil keeping it lubricated.
While this worked for my problem, it might not work for yours.
But what do you have to lose? You can't break broken after all.
M