Help adjusting Napa floor jack wont switch fast to slow

[loosanarrow]

New here. A buddy has a Napa 3-1/2 ton 791-6425 floor jack that will go up in fast mode, but does not switch to slow mode once it starts lifting. It has 3 larger “ports”, i think the far end larger port has a plug with another screw under it. There is a fourth smaller port to the far right.
They are labeled “do not adjust” lol. But it doesnt work so we played with the one that is far left counting turns so we could return to starting point. We did get it to switch over a couple times, but not consistently.
Anyone have any help getting this thing working? I did PM a member here, but no response, and even if that member saw my message, it is a lot to ask of someone to guide us through this, but I thought I would see if anyone could give us some direction. Tha ks!

 

[vwpieces]

Floor Jack Won't Lift? Here's A Quick Fix » NAPA Know How Blog

Discovering your floor jack won't lift is no way to start a DIY project. But fixing it may only take a few minutes if you follow these steps.

knowhow.napaonline.com

 

[IndyGarage]

I bought a Napa 3 1/2 ton jack about 3-4 years ago. It's low profile and got the fast lift. I've had the same problem somewhat. I put more oil in it and it seemed to help.

Honestly it's not as good as the Harbor Freight jack I bought last summer. Looks prettier though.

 

[RTM]

There is also an Imported Jack Repair thread that may have your answer.

Overseas Jack Rebuild Help Tutorial.

Well after numerous requests ive decided to put together a tutorial that will assist you do it yourselfers resurect/maintain your Taiwan Jack. This tutorial will cover the Main version of these jacks and i will try to include any variances that you might encounter. Again your jack might be...

www.garagejournal.com

 

[Hiball]

Sometimes there isn’t anything that can be adjusted, It’s possible that the Main Piston seal is kaput, If the overload was too light it would also prevent it from lifting a load, if the valve components are out of order or full of **** they can be problematic. In regards to the “do not adjust” valves one of them controls when the High side bypasses and the other one is the Overload that prevents cylinder pressure from exceeding the seals capacities. If you overtighten the High side, you will send too much pressure into the center quick lift tube and rupture it, If you overtighten the overload it won’t cause problems till you attempt to lift something above the jacks rating. It’s why they put them little stickers on there.

Hope this helps.

 

[loosanarrow]

Thank you guys!
We messed with it a bit today but were not able to get working right. It goes up fast, but then when hits a load, it gets very difficult to pump. It did just randomly switch to slow lift once, but then I let it down and tried again and it would not switch over again.
We discussed the possibility that it just may be too complex of a device for our simple country folk educations. Then we started looking at what we could salvage, casters, big bolt, pipe handle…
In the end we decided to try again next week before we give up.
Thanks again!

 

[Hiball]

Thank you guys!
We messed with it a bit today but were not able to get working right. It goes up fast, but then when hits a load, it gets very difficult to pump. It did just randomly switch to slow lift once, but then I let it down and tried again and it would not switch over again.
We discussed the possibility that it just may be too complex of a device for our simple country folk educations. Then we started looking at what we could salvage, casters, big bolt, pipe handle…
In the end we decided to try again next week before we give up.
Thanks again!

Sounds like the High side bypass is set too tight and it’s trying lift a load via the small quick lift tube, Do not force it as it will rupture that tube.

I’d like to add, there really is no switch to low/power side, it’s a single pump so it’s always working.

 

[loosanarrow]

Thanks Hiball.

Any idea which of the four screws is the high side bypass?

We found that the far left (looking at it while pumping the handle) one is a plug with an adjustable screw under it, the next two appear to be just oring fitted without another screw underneath, and the forth one all the way to the right is a smaller diameter than the rest.

 

[Hiball]

Thanks Hiball.

Any idea which of the four screws is the high side bypass?

We found that the far left (looking at it while pumping the handle) one is a plug with an adjustable screw under it, the next two appear to be just oring fitted without another screw underneath, and the forth one all the way to the right is a smaller diameter than the rest.

I believe the far right is high side bypass, should be easy to check. If you back it off too much you will lose the quick lift, you want enough seat pressure that it holds the lift arm and doesn’t fall under its own weight.

 

[loosanarrow]

Thanks again sir! I will go over there Monday and see what we can figure out.

 

[loosanarrow]

Posting about the the thread lock today reminded me of this old post which was the reason I joined the forum.
Want to thank hiball- with that information my buddy and I got his jack working like a charm. Much appreciated.