Thanks to @
Wilburn Cox for introducing this thread, and to
Ford850 for the explanation; never knew they were adjustable
It takes several hundred pumps to grease my walk-behind, and with how easily it popped off it took one hand pushing on the coupler just to get some grease in. It wasted a lot, took a lot of clean-up, and way too much time to get done.
I saw the knurled piece on mine had no gap to the body - couldn't see threads - and would not loosen by hand. But it came loose in a vice, with a lot of force.
Wilburn Cox, at 73, I'm not far behind you!
Since it wouldn't hold on a zerk though fully tightened, I took it apart. It's a 3-jaw type, and took a lot of fiddling to get it back together. During those attempts, I noticed one end of each of the jaws had a shiny spot. Not like noticeable wear, but I flipped them 180 to re-assemble anyway. That made all the difference.
When it was back together, I thought I had messed something up because I couldn't close the gap at the threads - the jaws were as far closed as they'd go. But, they could be opened farther, and easily locked on a zerk - tight enough so it couldn't be popped off, and the knurled piece rotates easily for adjustment, like
Ford850 said.
Apparently there is so much mechanical advantage in the assembly that those little shiny spots were enough wear to reduce adjustment range. So if yours has similar symptoms and you can't readily buy the "lock'n'whatevers", give this a try.
