The JLG 40F Boom Lift Dilemma

[Nahuel]

Trouble with auxiliary pump on jlg 80 hx

Hello! Im new on this... actually i need to know where the problem is on my man lift jlg 80 hx. Everything is working, all functions...but the auxiliary pump (12VDC) doesnt make the boom lift go down, or up, nothing...just makes the telescope in or out. For legal certification i need the auxiliary pump working on 100% functions... Please, i dont know how to make it work... can you tell me where i can start searching and testing?

Thanks a lot for your time!

 

[OFF]

Hello! Im new on this... actually i need to know where the problem is on my man lift jlg 80 hx. Everything is working, all functions...but the auxiliary pump (12VDC) doesnt make the boom lift go down, or up, nothing...just makes the telescope in or out. For legal certification i need the auxiliary pump working on 100% functions... Please, i dont know how to make it work... can you tell me where i can start searching and testing?

Thanks a lot for your time!

Welcome
what needs to happen for the boom to react to the aux. pump - the aux. pump needs to produce enough pressure to overcome/open the holding valve on the boom lift cylinder. The boom lift holding valve "release pressure" is probably a little higher than the other functions like telescope. Step 1 is to attach a pressure gauge to the system (should be test ports you can hook into) and make sure the aux. pump is producing it's rated pressure. If it is not making enough pressure, there might be an adjustment on a relief valve or you might have to replace the pump. You should be able to find specs for all this stuff in your manual. You can download a manual for the 80HX from the JLG web site if you don't have one.

I question whether the aux. pump will ever "lift" the boom. If it does, it will be very, very slowly. And make sure your battery is in really good condition. It's going to be 30 seconds before you see any movement at all.

 

[Nahuel]

Welcome
what needs to happen for the boom to react to the aux. pump - the aux. pump needs to produce enough pressure to overcome/open the holding valve on the boom lift cylinder. The boom lift holding valve "release pressure" is probably a little higher than the other functions like telescope. Step 1 is to attach a pressure gauge to the system (should be test ports you can hook into) and make sure the aux. pump is producing it's rated pressure. If it is not making enough pressure, there might be an adjustment on a relief valve or you might have to replace the pump. You should be able to find specs for all this stuff in your manual. You can download a manual for the 80HX from the JLG web site if you don't have one.

I question whether the aux. pump will ever "lift" the boom. If it does, it will be very, very slowly. And make sure your battery is in really good condition. It's going to be 30 seconds before you see any movement at all.

Thats was a fast answer!
I im going to try what you say, it has much sense.
Thanks so much for your help, im going to try it now, and i will tell you what happened at all...
Have a nice day!

 

[willie59]

Can you use the auxiliary power to operate boom down from the ground control station?

Also, will aux power operate boom swing from platform and ground controls?

 

[suite1010]

Hi guys I am back again in hopes for some help! last time I was here I couldn't get the telescope function to work on my jgl 27-32 so here is where I am and I need to see if you can tell me what I need to replace, I found out that the valves are not opening or closing Everything seems to be working because the valves are being magnetized but I am not getting any fluid flow to the cylinder so I put the hoses o a different bank and the telescope worked! Could the valves be stuck or bad or what and How do I get them off if so?

 

[OFF]

Hi guys I am back again in hopes for some help! last time I was here I couldn't get the telescope function to work on my jgl 27-32 so here is where I am and I need to see if you can tell me what I need to replace, I found out that the valves are not opening or closing Everything seems to be working because the valves are being magnetized but I am not getting any fluid flow to the cylinder so I put the hoses o a different bank and the telescope worked! Could the valves be stuck or bad or what and How do I get them off if so?

Sounds to me like the "dump valve" for that valve bank is not operating. A dump valve is a valve that dumps hydraulic pressure back to the tank until it is need by a function. What other functions are on the same valve bank as your telescope? Do these other functions work? If so, what happens when you activate another function on the same bank and the telescope? Does it work then?

If there are no other functions with the telescope bank that are working, trace the supply hose to that bank back until you find the dump valve. It will look like a block with a pressure relief adjustment on it, and solenoid coil.

 

[suite1010]

Dump Valve

Sounds to me like the "dump valve" for that valve bank is not operating. A dump valve is a valve that dumps hydraulic pressure back to the tank until it is need by a function. What other functions are on the same valve bank as your telescope? Do these other functions work? If so, what happens when you activate another function on the same bank and the telescope? Does it work then?

If there are no other functions with the telescope bank that are working, trace the supply hose to that bank back until you find the dump valve. It will look like a block with a pressure relief adjustment on it, and solenoid coil.

Yes sir everything else works and functions properly but what I did is to take the two hoses off (Telescoping) and I put the telescope out line on the lift cylinder and left the other side off and let it squirt fluid out and it worked great!

 

[willie59]

I know nothing about a 27-32, but maybe a totally failed telescope cylinder piston seal? Maybe?

 

[suite1010]

No sir it's not because when I hooked it up to a different bank it all worked. In other words I moved the hoses around to test the cylinder piston and be sure it was ok

 

[suite1010]

Jgl 27-32

No sir it's not because when I hooked it up to a different bank it all worked. In other words I moved the hoses around to test the cylinder piston and be sure it was ok

Willie59 and Off thank you guys so Much for all your help everything on my boom is now working thanks to you two! I was lost when I started on this thing and now I can do just about anything to it! Here are pics of the only other one I can seem to find like mine, It seems JGL is pretty proud of it to because this is theirs and it is in their personal collection! It is somewhere between 1965 and a 1968 Model! I plan to try and make mine look just like this one!

 

[OFF]

Hey Suite, thanks for the history lesson! I had never seen or even heard of a 27-32 before you showed up with one. That's the color scheme all JLG's wore when I started working on them in 1980. Glad everything worked out for you.

 

[Komatsumech]

Hello gentlemen ,
I am the proud owner of a well used JLG 40 ... I am going to assume it is a 40f but no where does it give a letter designation ... I don't have any photos .. but I will get some .. it has a Wisconsin vh4d ... looks like a long block was put in .. the sheet metal is the same color as the machine and the block itself is a dark metallic green color ... it has racine bang bang valves so for sensitive work you have to idle it down ... but its light weight well made simple basic and inexpensive ... I am looking for manuals and possible parts sources .. all functions work as they should with the exception of travel power ... it does have a two speed .. pulls the engine down something terrible in high range even on flat surfaces .. In low range I don't expect it to drag a trailer behind it but it seems to me it should at least have enough oooomf to climb a landoll trailer to haul it ... I tried giving the relief on the valve bank a tweek to see if it improved ... other function on that pump section seem to work as they should so I don't think its a pump wear issue ... Some of you guys are virtual authorities on these things and any help is appreciated .... I suspect a seal in the swivel could be bypassing .. I am under the impression there is a cross over relief of some sort in the drive system because with one wheel off the ground it still tries to pull on the weighted wheel .. could there be an issue there .. My expertise as you might say it in construction equipment and quarry toys ... thank you again Ralph .. ps. I wont be this formal again ..lol

 

[Komatsumech]

Nope thats all JLG .. Mine is identical only things missing are the steel tower that protects the joystick and the rubber boots to keep the critters out of them ... only way to slow down the functions is rpm control unless you want to plumb in a proportional flow valve ... which is a good option really and the necessary controller and proportional joysticks ... I am guessing we have very early models .. I bet yours doesn't have the belt driven alternator either ... I will post some photos of mine .. I'm new and not sure exactly the process of putting photos up so ... nothing like a short learning curve

 

[Komatsumech]

oh well that didn't work ... that last post was directed at the last page photos of the joystick with the micro switches .. now I need to find a 10 year old to show me how to post that reply with the reference ..

 

[OFF]

Welcome Ralph, did you try using the "Reply With Quote" on the post with the picture you were trying to show? it should have worked.

The biggest thing with your drive is engine RPM. Try to get a tach working on that engine. I'm thinking it's 1600 rpm on low, 2400 or 2800 on high. They don't climb or travel like the new machines, that's for sure. Does high drive bog the engine in both forward & reverse or only one direction? If it's only one direction, I'd suspect a weak coil not opening the valve fully.

 

[Komatsumech]

Welcome Ralph, did you try using the "Reply With Quote" on the post with the picture you were trying to show? it should have worked.

The biggest thing with your drive is engine RPM. Try to get a tach working on that engine. I'm thinking it's 1600 rpm on low, 2400 or 2800 on high. They don't climb or travel like the new machines, that's for sure. Does high drive bog the engine in both forward & reverse or only one direction? If it's only one direction, I'd suspect a weak coil not opening the valve fully.

It does it both ways ... and its possible the rpm's might be low ... ill stick the old photo tach on it ... it just gives up on a pull... almost stops pulling down the engine when it does ... very distinct difference in how the ...boom up ... function pulls the rpms down vs travel... something else mine has that I haven't seen on any other ,, it has a brake on each steer wheel .. looks like a trailer brake they put a spring applied hydraulic cylinder on ... when you travel it releases the brake when you stop the spring reapplies them ...

 

[OFF]

It does it both ways ... and its possible the rpm's might be low ... ill stick the old photo tach on it ... it just gives up on a pull... almost stops pulling down the engine when it does ... very distinct difference in how the ...boom up ... function pulls the rpms down vs travel... something else mine has that I haven't seen on any other ,, it has a brake on each steer wheel .. looks like a trailer brake they put a spring applied hydraulic cylinder on ... when you travel it releases the brake when you stop the spring reapplies them ...

The 40F had spring applied, hydraulically released outboard, dry disc brakes......on the drive wheels. Nothing on the steer wheels. Your machine isn't 4wd is it?

The only time I've seem a 40F bog down when you shifted into high drive turned out to be a problem with the drive valve not opening fully, causing the added flow of high drive to "dead-head" and almost stall the engine.

 

[willie59]

Sounds like he's describing a 4WD to me as well. And if I'm reading his last post correctly, when pulling a steep grade, at a certain point the engine RPM stops dropping and holds but the drive just falls flat out. If that's so, may be less of an engine problem and more of a drive circuit problem. However, as was stated by OFF in a previous post, the 40F was never a machine that could "climb a tree if it could get a bite on it".

 

[Komatsumech]

Sounds like he's describing a 4WD to me as well. And if I'm reading his last post correctly, when pulling a steep grade, at a certain point the engine RPM stops dropping and holds but the drive just falls flat out. If that's so, may be less of an engine problem and more of a drive circuit problem. However, as was stated by OFF in a previous post, the 40F was never a machine that could "climb a tree if it could get a bite on it".

Willie thank you .. no its 2wd but on the front steer wheels it has a individual hydraulicaly released brake... I really need some pictures

 

[Komatsumech]

Sounds like he's describing a 4WD to me as well. And if I'm reading his last post correctly, when pulling a steep grade, at a certain point the engine RPM stops dropping and holds but the drive just falls flat out. If that's so, may be less of an engine problem and more of a drive circuit problem. However, as was stated by OFF in a previous post, the 40F was never a machine that could "climb a tree if it could get a bite on it".

I suspect as much on the drive issue .. and those are precisely the symptom as you described it ... I am talking about loading on a landoll trailer that is maybe a 15 degree slope ..