whats wrong with my jack?

[Lmcclure]

not really a new one, they were throwing it away and im "thrifty" so i took it, its a 3.5 ton ac delco jack and i figure i could get it working...

what its doing

it will jack all the way up if i have nothing on it like nothin is wrong

if i try to jack anything up it wont go up if there is any pressure on it

if i have something up with another jack, i can place the delco jack under and it will hold everything up without letting go of pressure

wtf...

[htchbck]

Internal pressure bypass is not functioning right. No idea how to fix it though without looking at it. Basically its a pressure release that won't try to lift the jack if there is too much weight on it. Its usually built into the pumping mechanism, which is why if its all the way up already and you put weight on it, it will stay up. However, if you are trying to lift anything, the malfunctioning pressure relief is bleeding off the pressure. Hope that description helps a little.

[Safety Guy]

Weird. I guess this involves the mysteries of...

HYDRAULICS!

Or voodoo.

Sorry I can't help with more than cheesy comments.

Karl

[Lmcclure]

thats the thing, it doesnt have to be all the way up to hold firm, it can be less then half way and it holds firm, or anywere inbetween full lift and minumal lift

[walth]

tell you one thing, I wouldn't trust it until you figure it out!! yikes. look for some online manuals or go to that brand site and hope for a manual, etc.

and it is odd but I'm with everyone else, I have no idea

[zoom zoom]

I've got 2 like that, with one of them I took the oil screw out of the side and dropped transmission fluid in it, it worked like a dream for a couple days..probably 5+ lifts, then it went back to the same old not jacking up routine. Wish I could fix one of em, atm I'm reduced to the old factory crank em ups..

[htchbck]

What I already told you is correct... the pressure limiting device (however it functions) is most likely incorporated into the pump part of the jack... therefore when you try to lift, it bleeds the pressure off if there is weight on it. However, the release valve (whatever it is on that particular jack) that you activate to lower the jack is working properly (ie. holding pressure). Basically since the pressure relief valve is messed up, the jack constantly thinks its trying to lift 30 tons if there is any weight on it. Therefore to avoid damaging itself, it just bleeds off all the pressure that would normally pass through the pump and raise the cylinder. But if there's not weight on it, the relief isn't activating. Once the fluid makes it through the pump and into the cylinder, the release valve (manual activated by the user) holds the fluid in the cylinder. I don't know how else to explain it, but thats whats wrong with your jack.

And like Walth said, don't trust it till you're sure its working properly. Always use jackstands when under a vehicle, but even when lifting its important to have safe, properly functioning equipment

and it is odd but I'm with everyone else (except htchbck), I have no idea

There I fixed it :lol:

[lil red rocket]

Ewe, that sucks zoom zoom

[walth]

haha, sorry htch I knew you offered the general consensus. thanks for the fix

[Lmcclure]

Ha, ok I'm going to tinker with it some, if I don't fix it I didn't do any harm, may stop by the oreillys and see if i can get a parts sheet for a new one and possibly get some new parts for it, thanks for the info

[htchbck]

Post up a pic or two! Is it just a standard kind with the slot where the handle goes in to lever to pump it up, then you take out the handle and hook it to some type of twist valve to lower? Its all going to depend on how much can be taken apart, but I'll put money on it involving a ball valve and a spring that is probably broken, allowing the bypass to relieve pressure at WAY lower levels than it should. All that valve is supposed to do is keep you from picking up something heavier than the jack can hold, but when it malfunctions it lowers the theoretical limit of what the jack thinks it can handle. Good luck on it though, if it comes apart to where you can get to the valve I have no doubt its repairable... some don't come apart though.

[Lmcclure]

this is the jack, its an ac delco 3.5 ton


here was the problem, should have took a before, in the picture the left (center) valve was bottomed out, looked at it for a minute, and grabed the tin cup that goes over the spring and noticed it was compressed and stuck in the tin cups, after the spring flew half way across the yard i picked it up, cleaned it up, pulled the valve out, stuck on the spring and "inovated" a holder for the spring and cup, after that it works GREAT

CUSTOM

[drddan]

Good fix to a really nice jack!

[Lmcclure]

ha, thanks dan, i plan on getting the right parts for it in a bit but it works great now

[walth]

that's awesome!! and it works? that nail may do the trick depending on how chincy the original part is.