Weaver WA-75 repair

[whateg01]

Last Friday, I purchased an old Weaver WA-75. No indication of an "A" or "B" on the cylinder, so I think it's an old one. All of the drawings and service information I have found online is for the "A" or "B", and there do seem to be some slight differences. Basic design seems to be the same, though.

Only problem it has, aside from a broken pedal return spring and one side of the handle being broken by the seller, is that it only lifts a few inches. The seller had a pickup jacked up when I arrived, but over the weekend we tried to jack a 15000# tractor up and it only lifted a couple inches. Then it acted like it wasn't sucking up any oil. Every once-in-awhile it would jack just for the last little bit of the stroke, but otherwise, it just acted like it was empty. It never leaked down, so whatever issue exists is in the pump.

I pulled the top and bottom plugs from the valve "assembly" and the screen had some junk in it, but it wasn't plugged. I'll mess with it some more tonight.

There have been several changes made over the years, but one thing I noticed is that all drawings I can find now show a vent for the reservoir. This one does not have a vent - only a pipe plug where the fill hole is. It looks original, paint matches the cylinder, so I have no reason to believe that is the cause of the problem. I wonder, though if the suction created by pumping fluid out of the reservoir doesn't have some effect on the pumps ability to pull fluid from the reservoir. Unfortunately, I pulled the cylinder before I thought of that. Again, though, I would be surprised of that is a problem.

The design of these things is impressively simple. I think HiBall has said it before. There is no separate tank. The reservoir is the space ahead of the cup. No springs inside the valve assembly, AFAIK.

Anyway, I hope to have this back together by next weekend so I can try it out again.

If anybody has any thoughts on why it would do what it does, I'll take 'em!

Dave

 

[469 runner]

Did you check the overload valve? It may just be out of adjustment. It would cause fluid to bypass and return to the reservoir.

 

[whateg01]

Did you check the overload valve? It may just be out of adjustment. It would cause fluid to bypass and return to the reservoir.

If it's the overload, it wouldn't be out of adjustment since it picks the load up a bit before it stops pumping. I don't see any mention of an overload on this jack, either.

 

[Hiball]

If it's the overload, it wouldn't be out of adjustment since it picks the load up a bit before it stops pumping. I don't see any mention of an overload on this jack, either.

The Overload and Release are one in the same, 2" from bracket to the 1st nut is a good starting point.

 

[whateg01]

I'm not convinced that the release is the problem. Thanks for confirming that, though. Makes sense.

Having had the valve section apart, I don't see anything to suggest that either ball was stuck in any one position. I don't see any evidence of dirt past the screen. My theory is that having had it on its side when moving, loading, unloading, etc. it probably got enough air in the pump to air lock. So, air on both sides of the suction check valve, both under some amount of suction, after pumping a certain amount, there was enough suction on the tank side to keep the ball down.

So, with the system sealed as it is, as the ram moves down the cylinder a given distance, the amount of fluid required to fill the added area behind the ram is greater than the amount required to fill that same distance in front of the ram, so a suction is created on the tank side. As long as there is no air in the pump, it's a positive displacement and it doesn't care. But once air gets in the pump, the air can expand to fill the pump area to equalize the pressure (suction) on both sides of the check valve. So, I'll get it back together and try harder to get the air out of the system.

That said, is it better to have that suction created when the jack is up, than to have positive pressure when the jack is down? I could lift it with the plug out, then plug it before lowering it back down. Seems to me it would be better to have a suction there so as to reduce the chance of seepage past the packings at the top end. Maybe not?

Dave

 

[whateg01]

Cleaned everything up tonight. Was able to clean up the s/n so it could be read. Ended up putting both the top and bottom plug in the lathe and cleaning up the faces. The top one had a bit of a gash across it, which explains why after we pulled it out, we couldn't get it to seal back up. some fluid in it and got all the air out from behind the cup. Then started working the pump. There was a lot of air in it, and much of it wouldn't come out until I tipped the cylinder up. So, I believe that when it was being handled before, some air got into the bottom of the valve assembly, then just kept recirculating until much of it was in the pump, from there, it seems it's pretty difficult to bleed it, so I think it's going to work much better this time.

Dave

 

[whateg01]

Well, I got it back together and back under a load and it does pretty much the same thing. But this time after it quit pumping, I pulled the fill plug and it started giving us about a half-stroke of pumping. First half of the stroke felt like nothing, then it jacked the tractor up. So, I still think it has to be air. Since the overload is after the pump, if it was leaking, the tractor would have been coming back down between strokes. My best guess is there must still be some air in the pump, or the lower ball isn't coming off the seat until mid-stroke. I'm kind of at a loss here.

Dave