Pallet jack not holding pressure, moving shop this week, help!

[sheys]

Last week I stupidly did a bit of tune-up work on my old but adequate pallet jack. As long as i'd had it, the release handle had never been properly adjusted so I went ahead and set it properly. In the process I accidentally popped out the release plunger (for lack of a better name) and spilled a bunch of oil. No biggie, cleaned things up and put it back together, seemed to be fine. Today however, I went to pick up something heavy and no dice. Once more than a small amount of pressure is in the system the oil leaks right past the check valve. I took the valve assembly apart to inspect and clean and when back together things got even worse! Now I can't lift anything.

My main issue with this is that I'm moving my entire shop THIS THURSDAY. I need to get this fixed ASAP. There isn't much online about fixing pallet jacks, I'm hoping someone here can help.



The pics show the main check valve assembly out of the casting and the pump from both sides. Did I lose a part? Why is my check valve not sealing all of a sudden? I've had the thing apart and back together half a dozen times and the performance is always the same so I suspect dirt isn't the issue. It pumps up fine until there's load on it.

Next time I will leave well enough alone!

 

[BobRenz]

Off the top of my head -- your photo shows a heavier spring under the valve than on top of the valve - maybe the heavier spring should go on top?

 

[sheys]

The springs are definitely where they were, I did manage to keep track of that.
I realize there is another check valve in the system between the main cylinder and the pump cylinder but I'm not sure how to get to it. Seems like both of them would have to have issues for the thing to do what it's doing. Based on this animation:
Hydraulic Jacks Home Page Information Archive/Inside A Bottle Jack Animation Page

 

[surplusjohn]

make sure you have enough oil

 

[sheys]

make sure you have enough oil

I just accidentally overfilled it, definitely enough oil in there.

Now that I think about it more it seems like the tapered plug might function as both check valves in the same part (two tapered surfaces). Maybe it just isn't seating properly?

 

[Clive603]

Did you bleed out any entrapped air after re-filling?

Instruction manuals for some makes suggest that the handle needs to be pumped 5 to 10 times with the control in the release position to purge any entrapped air from the system after re-filling. Same manuals suggest that pump-up but unable to support load is diagnostic of air in the wrong place.

Clive

 

[sheys]

I'm pretty certain it's not an air issue.

I've had it apart a bit more and now things are even worse. I'm thinking that I must have lost a part.

Here is the main check valve assembly

Pump pressure comes from the right side and exits through the holes to reach the main cylinder. The tapered check valve sits against a not very tapered seat inside the part on the right. There isn't a lot of contact area to produce the seal.

The thing won't come close to picking anything up at this point and leaks back down to zero rapidly without any load. There is a huge leak somewhere for sure.

 

[sheys]

Actually, I take that back. It sounds like it's pumping a fair amount of air as well as leaking internally. With the fill plug open I can hear air bubbles when pumping with the handle pulled in. Nothing I do makes it go away.

 

[scojen]

Your in Brooklyn for heavens sake you got to have a friend in the trade or a neighbor with one.

 

[sheys]

I thought for sure this would be a simple fix but yeah, I am on to plan B. No parts diagram + no time + Christmas = throw in the towel. I've got enough oil on my clothes for one day.

The most annoying part is that I have a forklift downstairs on the dock but it's too heavy for the freight elevator!

 

[Ralph_P]

You show the same tapered check valve in 2 different locations. Is that the problem?

 

[Ken hosford]

It is ether leaking past check valve or the o ring around out side so replace o ring and lap the valve with the finest grit lapping compound , damp Ajax cleaning powder, tooth paste buffing compound . Or to heck with it and figure out way to jam some thing in jack when it is up

 

[Ron of Va]

I have never had a pallet jack apart, but I have taken apart a couple of floor jacks, and bottle jacks. They all had a ball bearing in the check valve system somewhere. I don’t see a ball bearing in any of the photos.

 

[Capp48]

Rent a pallet jack. Move. Repost your problem when it is not such a big deal. Buon Natale. Ciao.

 

[bran1har]

Here is how to fix, probably the u cup seal on the end of the piston.

https://youtu.be/MDG1L7CRbMk
How to Fix a Pallet Jack that Wont Stay up and Leaks Down Easy Fix - YouTube

 

[Tony Quiring]

You may have lost a ball.

We got a jack for a few bucks because it did same.

Starting removing simple things and noticed that there did not seem to be a check ball where one needed to be.

HD a bottle of assorted little steel balls from estate sale, found one that fit and working fine.

Yours may have fallen out when you removed parts, they roll far...

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