Hey all, I recently purchased a 644B that has been sitting for.... at least 3 years - possibly much longer. I just had the injection pump rebuilt to get it running again and now am working through some other issues and am wondering if anyone has input. 1. When I start it, it takes maybe 30 seconds before the hydraulic functions will actuate. You can hear the engine load a little, like the pump took that long to build pressure. Not sure what to make of this as there are no electronic controls that do anything like this. 2. The steering is "bucky" - seems the worst in crab steer mode. The wheel bounces and fights being turned. Its worse the faster you try and turn it. 3. Fully boomed out at 0 degrees (angle not temp) - I can't raise the boom unless I give it some throttle. Boomed in I can raise it at idle, though slow. Similarly I seem to be fighting the counterbalance valve on the fork curl function - at idle it will move in one direction, but needs some throttle to move the other direction. I did put almost all new hoses on it, and it sat for so long I am sure the system has/had air in it - but I have run it quite a bit now and haven't seen a ton of improvement. 4. I haven't got the transmission to shift. It feels weak. Has trouble getting over minor bumps. I will preface this one by saying I changed the oil and pulled the filter and the filter was awful. The oil was dirty but no water or metal in it. I didn't have a new filter and needed to move it so I cleaned the old one best as I could and put it back in. I have a new one arriving this week. I assume that could cause the issues I am seeing. 5. I am having a bunch of issues with the frame leveling. someone previously disconnected the front cylinder. Fearing it was full of water or something I took it apart. The inside is fine but one counter balance valve was rusty. I have a new one ordered. Twice now i have suddenly had the frame lean all the way to one side while I was playing with the steering - not even touching the frame control. I don't see how these systems are interconnected. I have never owned a telehandler before and have limited operator experience so hoping some of you can maybe offer some input.
Hi sir. It seemes that your hydraulic system is starving , there should be a screen in your hydraulic tank , check if its not blocked. NormalLy if machines are sittting for a long time they get some sludge build up in the hyd system and that is funerable for screens and filters. Even if your oil looks clean , just go trough your filter system
I went all through this with my 844-42-C sounds like your relief valve pressures are off too low. Same with steering pressure. Idk on your but the 844 has test ports under the seat area where you hook up a pressure gauge 5000 psi and set pressures for the 2 main relief valves on valve block. Yours may be different but it's a similar procedure gotta adjust the relief valves to spec to work together.
On the frame leveling on its own you might check the control valve maybe seals bad and it bypasses fluid possibly why they disconnected front cylinder.
Thanks for the replies. I did clean the hydraulic tank out before I ran it. I pulled the cover off the top, fearing there could be water or sludge in it. It was very clean. The pick up screen had fallen off, so I got a replacement and installed that. So I know there is nothing restricting the pick up. I have a pressure gauge but need to get the correct quick connect for the pressure ports. My *guess* as to why the front leveling cylinder was disconnected is one of the counterbalance valves sits in a recess that points upward. It fills with water in the rain and the whole valve was rusted. I am lucky I was able to get it removed ok. I am thinking it jammed up and wouldn't move and caused the frame to not be able to tilt in one direction. JUST A GUESS. I wish this thing could talk. I have zero history on it past it looks like it sold at auction in 2008 in Florida. Somehow it made it to Minnesota now. Bought it with the story the fuel tank had gotten algae in it and fouled the injectors. Someone had put injectors in it and it would run but wouldn't start without ether. Ended up having the pump rebuilt and new injectors. The fuel tank was very sludged. I got that all clean now. The transmission wouldn't engage when I got it but that turned out to be an electrical issue. It had been really cobbled on the wiring. But bottom line - I don't know why someone parked this machine.
On these Lulls if you don't have full hydraulic pressure light goes out on transmission they won't go into gear. Mine also has hydraulic E brake needs to be off to go into gear.
There is a procedure to adjust the relief valves such as checking pressure while extending boom, checking steering port pressure etc. it's usually around 3000 psi max. You don't want too much will over pressure system or not enough won't lift anything heavy etc. The Lulls use a dual pump when I got my 844 42C only had steering nothing else no boom wouldn't go into gear The PO ran the pump too low destroyed the seals in 2nd stage pump. I just ended up getting a new after market pump they had to custom make it took 2.5 months but was reasonable $1300 but even after installing everything was weak would drive though I found a relief valve stuck open with plastic seal from the pump causing problems.
I saw your post about the relief valve stuck. Thanks for posting that. I wish more people followed up like that. I did pull mine out today to inspect. It looks different than yours. I didn't see anything lodged in it. I also pulled the high pressure filter out. Could use a new one but wasn't awful. Some sludge but no metal or debris or anything. At this point I need to get the fittings to attach my pressure gauge I think and see what I am actually getting for pressure. Will report back...
There are 2 types of hydraulic systems with these Lulls one is mid inlet which is probably on yours so different than mine. But you probably have 2 relief valves. Each set of valve blocks usually have one. You can check that the relief valve functions properly by depressing it with a tool should have firm resistance but smooth.
Screwing around a little more with this today - I threw a pressure gauge on one of the aux quick couplers and I get around 2500 psi at idle. I am not a hydraulics wizard - but looking at the drawings in the manual it looks like there is a main pressure relief set at 3175 psi. I am wondering if this is what I should be seeing on the aux line? The counterbalance valve from the front frame leveling cylinder is stamped 3500 psi - this is higher than the system pressure. Does this seem correct? I have no reason to believe its not the original valve. *****EDIT**** Answered my own question but will leave it here in case it helps someone else. Schematic shows it to be a 3500 PSI valve. I think I am thinking about this wrong. 3000 PSI acting on one side of the cylinder will generate well in excess of 3500 psi on the opposite side - thus opening the valve. Someone smarter will hopefully correct me if thats not how these work.
That's the max pressure rating of the valve doesn't have anything to do with system pressure settings.
There should be a block of test ports to check pump 1, pump 2, steering pressure etc. That's where you need to test pressures at.
Test ports
The system will have an idle pressure and max pressure when at high rpm's.
I ordered what I hope is the correct (PD242) coupler for these last night. Supposed to be here next Monday... Hoping it shows sooner and I can see what I get. I just happened to have a spare quick coupler around that I had fittings to attach to my gauge so I thought I would make sure I didn't have super low pressure on that or something pointing to a pump being bad or something.
Ok but you have a dual stage pump one could be fine other low pressure. On my tilt cylinders there is a 12v solenoid on the back cylinder that locks it when boom is out certain length via hall sensor signal. You can check if it's getting power 12v with a power probe. By default it's locked and it unlocks to allow crane tilt if boom hall sensor detects boom not out past certain length.
Yeah that's it.
my experience with hydraulics was working on sweepers that use 12v direction solenoids these Lulls are total mechanical systems and complex took me a good month or so to figure mine out. Just takes time and unfortunately very few know how to work on these tractor mech Craig helped me out a lot.
I got impatient and made up an adapter to thread on in place of the quick connects. On pump 2 I get 2500 psi at idle- but only when I am actuating a function. When I try to roll the forks down or level the frame I get to a point and then my pressure drops, and I can't get it back until I re-center the control. Same thing happens when I stroke the fork roll cylinder all the way out and deadhead it. Its like over a certain pressure a relief opens or something. I have steady pilot pressure the whole time. I'm not quite following yet on the schematic how it sends pressure to that circuit only when needed. The steering is even more confusing. I don't know if that is related or not. It steers fine in 2 wheel steer mode but roundor crab it will only steer a little bit before the wheel doesn't want to turn. Turing it super slow doesn't help. Steering pressure does drop to about 1000 when the wheel binds up - but doesn't go away.
Your steering should be 2200 min. You shouldn't have pressure drops when activating functions. Here are some test procedures on mine 844-42C it's very similar to the 644 but yours may be different
Here
Here
After I set my pressures with 2 relief valves my front forks would only go down not up. Took spool apart on valve block for forks cleaned it was fine after. You prob are losing pressure somewhere in system relief valve etc. Yours may have the mid inlet system which is different but this gives idea you need to find procedure for your model.
I basically took out every valve in the valve block checked seals on them etc. A bad seal could cause problems also.
Thanks for posting those. I wonder if those exist for my machine. I believe mine is the mid inlet. I have the spools up front and the manifold in the center near the accumulator.
There should be an adjustment test procedure for yours also.
Thats a control manifold system- not a mid inlet
I'm working off the service manual JLG has on their website. To me it appears to be what they are calling the mid-inlet. My machine is a 644B-42 serial 1136. It looks like the last control valve unit was 207. What I am not seeing in the manual is a nice step by step procedure for setting the pressures like roadoil posted for his C series machine. Are the relief valves I highlighted were the pressure for pump 1 and 2 are set?
Tractormech Craig was the one that sent me that test procedure I posted. This shows relief valves you need to inspect.
That needle inside relief valve was binding on mine I cleaned it up some with fine sandpaper. Be careful these are very expensive from JLG new $3500 and used from these scrappers like web equipment $1500 so don't lose parts or order when taking apart. I found and replaced mine with same models Gresen and Husco cheap new from regular parts suppliers old stock. One was for a Cat but same relief just different factory set for pressure. You gotta adjust them anyway even if a JLG apart because of system wear changes pressures.
You need to start with a baseline take pressures on all here full Throttle and record. See what you are dealing with.
You're correct- I just looked at it quickly and misidentified it. Sorry for the confusion
Those are the relief valves for pump 1 and 2
Sent you a pm
Progress update. - Got my test coupler Friday. Ordered one off Amazon. The damn thing is so far out of tolerance it wouldn't even work until I took it apart and ground some off the front of the sliding collar. It wasn't coming forward far enough to hold the locking ball bearings down and the thing would just pop right off. Now it sort of works, pops off and sprays oil on my boot half the time. Pretty disappointed. Lesson learned to buy something better next time around. -Pulled the relief valve for the carriage tilt/frame leveling circuit apart. There is a seal in the end of it that is damaged. I am going to have to explore my options on this one. Looks like there was a seal kit available once upon a time but not seeing that part number come up online. I see similar HUSCO valves for sale in different pressures. I have a couple resources I can reach out to for ideas on this. I think this makes sense why I can't get the frame leveling and carriage tilt to work well. I can only get about 1200 PSI before this valve opens. - Screwed around with the steering some today. What I found is I am only getting about 1000 PSI on the steering. I jacked the back axle up and with no weight on the rear wheels it steers fine in all modes. The way they have the cylinders in series when its in either of the 4 wheel steer modes makes me think with the low pressure I am just not getting enough to operate all the cylinders. Whats kicking my ass a little though is where is the steering pressure set? The manual says 2200 PSI is the proper reading - but doesn't say what to check if its low. It appears there is another relief valve in the control block - but this is set to 2450 and the manual specs 2200 max for the steering. It looks to me like the steering is coming off pump 1. Pump 1 test pressure is around 2500 PSI. I am leaning toward there being something going on in the control block. -Brakes and accumulator I was getting 0 PSI. Confused about that one but leaving that be for now. The brakes do sort of work on the machine, but not what I would call well. Have some work and travel plans now so it will be a bit before I can dive back into this. Thanks for all the help so far!
As long as it's a Husco 4545B it's the same but factory set pressures different for various applications Loosen locknut set pressure with hex key. Your pressures too low with relief valves. Bad O ring on valve can cause issue go to hydraulic seal supply or measure go to Hercules or rocket seals or O rings and more order new.
We have a hydraulic sales rep at the plant I work in. I shot him an email this morning asking for some advice. He also suggested Hercules and pointed me to a few seals I can try. I need to measure it and see what they have that might work. I'll report back in case it helps someone else. He also thought I can likely buy a $60 1800 PSI valve and put my spring in it. Like I told him, often there is some off the shelf solution for these old/obsolete/over priced parts - but sometimes its hard to get there without specific knowledge and experience.
Someone on a hydraulic cylinder repair facebook group I am in sent me this - which I found helpful. The 51790 part number lead me to this place - Iron Wing Parts - Online Store In-Stock & Ready to Ship Heavy-Duty Truck Parts, Heavy Equipment Parts, & Industrial Parts. Easy Search & Buy. Free shipping on qualifying orders over $100. Same Day Shipping Available. 30-Day Returns. www.ironwingsales.com They have the seal kit for 16 dollars. Hopefully its correct. I ordered it, but will be out of town for a bit. Will report back if it is the right kit.
It's prob a Husco 4545B like in mine. But maybe the seal kit will work.
Yes usually off the shelf parts such as Sun valves but I found on my 844C some were proprietary made for Lull by various companies I think one was out if business. But these are common components for mechanical hydraulic systems and I am sure someone with knowledge could get a modern part in other brands that's the same.
Mine clearly has 5060 stamped into the side of it. The 4545 does look similar in the pictures online though.
Ok
Is the 5060 what's spec'd for your machine ? I have seen some hackery with sun valves that fit and look identical to what's supposed to be in equipment but totally different valve messing up the functions. Here is the 4545B old one I replaced.
Update - I got the seal kit. Installed it tonight and now I can set the pressure for pump 2. Once I got this set the frame leveling and the fork curl work properly! Does anyone know how to address low steering pressure? The manual tells me what it should be but fails to suggest causes and solutions.
Getting to the end of my list of issues on this machine, but this one is odd - The boom hoist circuit is weak in the UP direction - at idle I am getting around 1000PSI at test port 1. At full throttle I get somewhere around 2800. It struggles to lift the boom at idle with the forks on. If I bottom the hoist cylinders DOWN at idle I hit almost 3000 PSI. Kind of at a loss. I get 3000PSI if I bottom the boom telescope IN too. Is there a possibility the spool is worn or something? Anyone ever seen this?