Probably my last update on this.
No joy at finding the proper packing washers for the piston, so I had to improvise. The place in Seattle was good enough to work with, but they had no drawings anymore or any reference material and couldn't match up my dimensions. So I found some all-rubber spacer washers from something I can't remember in my tool box as excess parts so they were repurposed here.
To get an idea of the problem, here is a photo of the top case, the original packing washer on the right and the hard-case seal from the P51 kit in the center. As you can see, there was no way I could use that piston seal.
I didn't have to trim the inside diameter of the rubber washer I found, but I did have to trim the outside. To do that, I put the 3/8" thick washer on a pencil and spun it against a grinding wheel, which neatly burnished off the necessary diameter so it would fit into the hole and still accept the piston. Nearly all the rest of the parts from the P51K1 kit were correct enough to use, with the exception of one check ball as I recall.
I reassembled everything and bench tested it. The fluid pumped without any external leaks, so I was satisfied.
However, upon returning it to service, it would not raise the mobilizer once attached to the shelter. I could faintly hear it leaking internally. Dang!
Out it came. I figured I got the pressure relief set too light so I took off the top and adjusted it down, still no joy. I adjusted it all the way to put as much pressure on the relief as possible, still it was leaking, but I did discover it wasn't from the pressure relief. I checked for cracks and couldn't find any. Eventually I took it apart and found one of the machined surfaces for a check ball was corroded and wouldn't allow the check ball to seat properly. It was just enough that it could pump fluid without any real pressure needed, but once it needed a lot of pressure, it would bypass through that chip.
Well darn.... now I need to find a place to machine that ledge smooth again. I'm not sure I'll be able to have that done.
In the interim, I found several of these exact same pumps on ebay and purchased a handful. Interesting enough, most of them came from my Air National Guard unit, and had signatures on the inspection tags from people I used to know. That was a neat coincidence.
I have two of these shelter dollies (mobilizers), each taking two of these pumps. I now have enough spares to replace all of them. However, I'm in the midst of rebuilding a second one (from my first mobilizer) and then I'll see if I can get this bad housing fixed and complete the rebuild on it again.
Summary
The P51K1 kit has -most- parts needed for this pump, but most importantly it does NOT have the packing washers for the piston. I happened to have a rubber washer about 3/8" thick and a tight fit on the piston that I had to trim down to the proper outside diameter. That fit in the hole with the piston through it and the locking nut tightened in place. No leaks from that, but we did find an internal leak past a corroded check-ball land.
Thanks to the folks here, I took on this project and was pleased by the outcome, even if in the end I needed a new pump anyway.
Asa Jay
