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Old 09-03-2011, 12:37 AM   #1
honda1998civic
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Default How to adjust valves on Napa Professional floor jack model# 791 6425

How to adjust valving on Napa Professional floor jack model# 791 6425? Recently took this hydraulic unit apart to replace seals but the valves had already been adjusted all the way down.. Can I look at another similar unit and see how far the valves are out and just set mine the same way? How are these set?
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Old 09-03-2011, 12:43 AM   #2
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Default Re: How to adjust valves on Napa Professional floor jack model# 791 6425

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Originally Posted by honda1998civic View Post
How to adjust valving on Napa Professional floor jack model# 791 6425? Recently took this hydraulic unit apart to replace seals but the valves had already been adjusted all the way down.. Can I look at another similar unit and see how far the valves are out and just set mine the same way? How are these set?
Yes... You can use another Napa Professional Jack to get the proper setting, They are very sensitive in Low/High switching valves, To Light and it wont switch to the Low side and too Heavy and you lose the Quick Lift.
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Old 10-03-2012, 11:59 PM   #3
fdny136
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Default Re: How to adjust valves on Napa Professional floor jack model# 791 6425

anyone have this jack and can check the settings?
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Old 10-04-2012, 12:03 AM   #4
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Default Re: How to adjust valves on Napa Professional floor jack model# 791 6425

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anyone have this jack and can check the settings?
Does yours have 3 or 4 valve plugs on top? What have you done to need the Oem settings?
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Old 10-04-2012, 08:40 AM   #5
fdny136
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Default Re: How to adjust valves on Napa Professional floor jack model# 791 6425

.it has 3 valve plugs. I was rebuilding and my nephew tried helping an removed them.the jack is together and no longer leaking but I am not sure if they are set correctly.I believe I have them in there correct bore.this is actually a craftsman 2 ton aluminum.thanks

Last edited by fdny136; 10-04-2012 at 08:48 AM.
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Old 10-04-2012, 12:17 PM   #6
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Default Re: How to adjust valves on Napa Professional floor jack model# 791 6425

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Originally Posted by fdny136 View Post
.it has 3 valve plugs. I was rebuilding and my nephew tried helping an removed them.the jack is together and no longer leaking but I am not sure if they are set correctly.I believe I have them in there correct bore.this is actually a craftsman 2 ton aluminum.thanks
The 3 Valve units are fairly simple, Working from Left to Right.. If memory serves me correctly, The First valve plug is for the High/Low Changeover. The Plug on top is Nothing more than a Screw in Cover, The Adjustment is below that Plug. The Second Valve is what i call the Working Valve, There is No adjustment Here... The 3rd Valve is the Overload, This can not be Properly Set without a Load Station. If you have adjusted this Valve, Tighten it down completely and back it off "1 and a 1/2 turns". This is just a Preliminary setting to get you close... You need to make sure that whenever you are using your jack and intend on putting yourself in harms way that you use Jack Stands and always be mindful of what your lifting. Its a Safety Device to prevent the PSI from exceeding the Limit of the Seal.

Now How to adjust... Ive already told you how to adjust the Overload (3rd), There is no adjustment on the Working Valve (2nd) So the Main Adjustment is the 1st valve with is the H/L changeover valve. You just dont want to crank it down because this Valve affects where the Oil goes when the Jack reaches its Load. If set to light you can rupture the Inner Quick Lift Cylinder by sending the High pressure oil into it versus the Big Cylinder. I used to have some starting guidlines wrote down somewhere but im misplaced them. The best way to set this jack up is by simply using a little trial and error.. What your looking for is the Jack to Operate on the High side when "No" Load is Present, But switch over to the Low end when it reaches the Load. Underneath that plug is adjusting screw with a Big spring and a Ball/Cone sitting on a Seat. You need to adjust the Spring tension till you get a Nice Crisp Transfer from High to Low. It will take a bit of Time, Just Keep track of your revolutions and make small subtle changes. Hopefully this will help.. If i can be of further assistance dont hesitate to send me a PM as i dont always see every post.
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Old 10-04-2012, 01:29 PM   #7
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Default Re: How to adjust valves on Napa Professional floor jack model# 791 6425

Hiball - Could we get a picture of what the load station looks like? ..just curious.
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Old 10-04-2012, 01:39 PM   #8
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Default Re: How to adjust valves on Napa Professional floor jack model# 791 6425

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Hiball - Could we get a picture of what the load station looks like? ..just curious.
Ill try to remember to snag a picture next time im out at the shop...Really all it is is just a Steel Framed Unit (similar to a Press), at the Very top is a Cylinder that is filled with oil and at the end of that Cylinder is a Gauge that converts PSI to Tons (There is some Mathematics involved here that im not even gonna try to explain) When you load test a Jack, You simply place the Lift Arm under the Cylinder raise it against the cylinder till you get the proper reading on the Gauge, set the Overload and Retest. I have a Local Hydraulic shop here that doesnt work on Hydraulic Jacks anymore and i they take care of all the Mathematics and build these stations for me. This Setup also works very well for checking the integrity of a Hydraulic Jack and the Seals.
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Last edited by Hiball; 10-04-2012 at 01:54 PM.
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Old 10-05-2012, 12:15 PM   #9
fdny136
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Default Re: How to adjust valves on Napa Professional floor jack model# 791 6425

unfortunately my nephew removed the valves no I need to figure out where they go?
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Old 10-16-2012, 08:17 AM   #10
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Default Re: How to adjust valves on Napa Professional floor jack model# 791 6425

just like to say thanks to hiball and the other members here for all their help.my jack is together and works better then ever
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Old 01-04-2013, 05:53 PM   #11
hdrider2610
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Default Re: How to adjust valves on Napa Professional floor jack model# 791 6425

does anyone have a complete schematic of this unit? I have the same jack, unfortunately i barrowed it out it came back in peices barrower tried to fix it. I have been looking to fix it for a year and this is the first site with any info on this power unit. Thank you
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Old 01-04-2013, 06:30 PM   #12
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Default Re: How to adjust valves on Napa Professional floor jack model# 791 6425

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Originally Posted by hdrider2610 View Post
does anyone have a complete schematic of this unit? I have the same jack, unfortunately i barrowed it out it came back in peices barrower tried to fix it. I have been looking to fix it for a year and this is the first site with any info on this power unit. Thank you
http://mytoolservice.com/man/7916425A.pdf


Below is a bunch of Napa Jack diagrams if the above one doesnt match yours..

http://www.toolwarrantyrepair.com/?view=Manual
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