JLG 40HA drive issues - many hours of testing and still won't go - frustrated.

[Upta-Maine]

A long story that I will try to make short. The drive function slowly went away on our 40HA. A local hydraulic shop indicated they felt the pump was gone. They found a used pump with the same type of servo motor. We purchased / installed the used pump and the drive function was restored immediately. After roughly 6 hours of use the drive function has slowly gone away (both directions) and now the machine will not move. We took the pump out again and brought it to the hydraulic shop and they have confirmed that the pump is working correctly. We re-installed the pump and no drive functions work.
We have tested a bunch of stuff. First the yellow lead to the drive control has 12.5 volts when we step on the pedal. We have voltage on the BRN/BLU & BRN/RED wires from the control through the basket panel, through the main panel (16 & 21) and to the 4 wire harness at the servo motor mounted to the pump. The voltage goes up to around 8.5 volts (on either wire) when the wires are connected all the way to the servo motor. If we disconnect the harness at the servo motor and monitor the voltage we get around 12 volts on each wire when the controller is pushed forward and back. We took the servo motor and mounting plate off (looking at the bottom where there are four ports with O-rings around them) and operated the drive control. The metal bar in the middle port seem to move just slightly and vibrated when I put my finger against it. I would have envisioned more movement but maybe not. We put it back together and still nothing.
We are stumped. Things seem to be working the way they are supposed to but the machine does not travel in either direction. All functions work off of the outer pump (lift, telescope, steering, basket movement). The motor does not even bog down in the least when we try to travel.
Looking for any ideas beyond what we have tried already. Maybe there is an issue with pilot pressure....? It appears that the outer pump has a low volume line that runs to a regulator/solenoid on the wall of the engine compartment and then back to the main pump. Our thoughts are that the outer pump produces pilot pressure for the drive control servo motor that directs this pilot pressure to move the swash plate to the desired angle producing forward or reverse travel. Maybe we have a problem with pilot pressure?
Any help would be appreciated. We are scratching our heads on this one and getting really frustrated with the time we have put in and really nothing to show for it. We do have a hydraulic pressure test kit (previously used on excavators) that can be used for testing purposes if need be.
Thanks, Scott

 

[Upta-Maine]

I have carefully read through the following thread started by razerface:

JLG 40HA should I buy? Fixer-upper​

• Thread starterrazerface
• Start dateSep 24, 2010

A lot of great info in this thread. willie59, barklee and OFF all offered a ton of advice but unfortunately razerface never ended the thread so I could never learn what was the resolution to his problem that is very similar to our problem. Based on some of the info they needed to diagnose his issues I wanted to add more facts to my thread:

1) I believe our 40HA is a Ford powered lift with standard bang bang controls.
2) The serial number is either 009269 or 0300018841 (ID plate has seen better days) maybe manufactured in June of 1994 but not sure on that.
3) It uses the PQ Control M120 (at least the image of that control looks identical to what is there)
4) The servo motor on the pump has the typical 4 wire harness and it has the lever on the outer housing to override the motor and (supposedly) manually activate the swash plate.

We have tested the brake release lead coming out of the PQ control (BLK/ORN) and it does go hot (12 volts) when the control is moved forward or backward. We also checked this voltage at what we think is the brake release solenoid unit on the inside of the engine compartment and it is good. Also (not sure if this is a legitimate test) but we noticed that a metal wrench will stick to the top of the brake release solenoid when it is activate. The solenoid must create a magnetic field when it is activate since the wrench does not stick when the control is not activated. We don't think it is an issue with the brakes staying on because everything voltage-wise looks good and we would think that the RPMs of the engine would drop if the drive function was trying to fight the brake function.

Anyone feeling "charitable" and want to jump in to help give us some guidance or ask us for more info? willie59...? barklee....? Anyone....? Beuller....?

Thanks in advance for any help, Scott

 

[willie59]

It's been prolly over 15 years since I've worked on one of those machines, most certainly have forgotten much of what I know about them so I have little advice to give. But if I recall correctly, that little manual lever on the pump servo, with the engine running at idle you should be able to move that lever full in either direction and pretty much stall the engine from the brake being engaged. If it won't do that, or at least build substantial pressure moving that lever, then I would think you still either have a problem with the pump or pump charge isn't there if it uses external charge pump feeding the drive pump.

 

[Upta-Maine]

Thanks Willie59. When running the model code through the Sauer Danfoss pump manual it indicates there is a charge pump within the main pump. So my theory with pilot pressure coming from the third pump was incorrect.


Sorry it's up-side-down but it was tough to get the camera into position.

We definitely have tried the manual override lever on the servo motor and it makes absolutely no difference. The machine does not move and the RPMs do not change in the least.

Do you know any other members on this forum that have knowledge of the 40HA lift or even just the M46 pump?

Also - do you remember enough about the 40HA if I sent you some pics you could tell me what some of the things are in the engine/pump compartment? It's really frustrating not to know what a lot of this stuff is or why it is hydraulically connected to each other.

Thanks again for jumping in on this thread,

Scott

 

[willie59]

I'm not an expert on those pumps, but I know by experience that if you move that manual lever it should build pressure and load the engine because the brakes are engaged. If it doesn't, I don't know what is causing that.

 

[OFF]

I saw this thread but stayed away because I had nothing to add. I did work on a 40HA for years, and it did have an intermittent drive function problem that I never did find a cure for.

Maybe twice a year, usually on a hot day, it would just stop driving. Shut it down, come back the next day and it would drive away like nothing every happened. I never figured out what was causing it and it's always been a sore spot with me. I don't remember it happening anymore later in the machine's life, I think after changing the hydraulic oil it improved or even went away. No proof of that, just my thoughts.

 

[Upta-Maine]

We found the issue after a ton of troubleshooting (taking the pump on and off three times). It was a hidden (clogged) filter in the servo motor base assembly. If anyone needs more info comment on this post and it'll email me. I'll log back in and explain more with pics if need be.

 

[excavator]

Sorry, I missed your original post and just saw this today. Thank you for the update, it will help others in the future. Most, and I've been guilty of it also, don't take the time to follow up on what cured their problem. Thanks again.

 

[kmacomcoug]

Upta-Maine , i have a 1993 40 HA , no movement forward or reverse , same symptoms you had , but most all other functions work for the most part , some stop in partial travel , appears to be a hydraulic issue , where is this servo motor located with the filter , can you paste a photo of it , thanks in advance​

 

[kmacomcoug]

We found the issue after a ton of troubleshooting (taking the pump on and off three times). It was a hidden (clogged) filter in the servo motor base assembly. If anyone needs more info comment on this post and it'll email me. I'll log back in and explain more with pics if need be.

@Upta-Maine , i have a 1993 40 HA , no movement forward or reverse , same symptoms you had , but most all other functions work for the most part , some stop in partial travel , appears to be a hydraulic issue , where is this servo motor located with the filter , can you paste a photo of it , thanks in advance​

 

[Upta-Maine]

@Upta-Maine , i have a 1993 40 HA , no movement forward or reverse , same symptoms you had , but most all other functions work for the most part , some stop in partial travel , appears to be a hydraulic issue , where is this servo motor located with the filter , can you paste a photo of it , thanks in advance​

KMACOMCOUG -
I apologize - the forum used to notify me when there were posts on a thread I started. It never notified me of your post. Are you still having issues with the travel in your 40HA? If so I can get a pic tomorrow and post it.

Scott

 

[mclean]

I'd like to hear more about this hidden filter.. working on a m46 in an sd70 with no charge pressure.

 

[Upta-Maine]

I'd like to hear more about this hidden filter.. working on a m46 in an sd70 with no charge pressure.

mclean -

Looking from the end of the M46 pump find the servo motor that is used for travel control. On our M46 the servo motor was on the bottom but I have heard that these pumps can be mounted in any of the four possible positions. On the servo motor housing there will be a plug that can be removed using an allen wrench. Refer to the three pics below. These pics are at the same angle just taken as the camera got progressively closer to the filter location. I pointed out the plug in the pics with an arrow....hoping it comes through for you when you open the pic.

Once you remove the allen wrench plug there will be a small cylinder behind that. The cylinder will have threads inside that (on ours) will accept a 1/4" fine thread bolt. Use a long 1/4" fine thread bolt and thread it part way in. Give it a good pull and a cylindrical filter will come out that is about the size of a pencil and maybe 3" long.

After a lot of trouble shooting on our machine it turns out that, being the cheap bastards that we are, we used hydraulic fluid that was too thick (but it was free). It continuously clogs this filter. We can clean the filter but in 10 minutes of use the machine will no longer travel. We have temporarily removed this filter but be careful if you do this - the machine is waaaay too responsive with the travel now. We really should put seat belts in it when the filter is out because she takes off like a jack rabbit. Our conclusion is that this is not only a filter but also a restrictor plate of sorts. The machine operates much more normal when the filter is in and clean.

Hope this helps. Let me know if you need more info.

Scott

 

[kmacomcoug]

mclean -

Looking from the end of the M46 pump find the servo motor that is used for travel control. On our M46 the servo motor was on the bottom but I have heard that these pumps can be mounted in any of the four possible positions. On the servo motor housing there will be a plug that can be removed using an allen wrench. Refer to the three pics below. These pics are at the same angle just taken as the camera got progressively closer to the filter location. I pointed out the plug in the pics with an arrow....hoping it comes through for you when you open the pic.

Once you remove the allen wrench plug there will be a small cylinder behind that. The cylinder will have threads inside that (on ours) will accept a 1/4" fine thread bolt. Use a long 1/4" fine thread bolt and thread it part way in. Give it a good pull and a cylindrical filter will come out that is about the size of a pencil and maybe 3" long.

After a lot of trouble shooting on our machine it turns out that, being the cheap bastards that we are, we used hydraulic fluid that was too thick (but it was free). It continuously clogs this filter. We can clean the filter but in 10 minutes of use the machine will no longer travel. We have temporarily removed this filter but be careful if you do this - the machine is waaaay too responsive with the travel now. We really should put seat belts in it when the filter is out because she takes off like a jack rabbit. Our conclusion is that this is not only a filter but also a restrictor plate of sorts. The machine operates much more normal when the filter is in and clean.

Hope this helps. Let me know if you need more info.

Scott

Upta-Maine​

Thank you for responding with this information , my machine set up is slightly different , it does not have a manual lever on the pump servo that I can see anyways , not sure what its supposed to look like. I have attached some photos of what I have , the location of the plug for the filter on mine if I'm at the right location looks like has a plug that is removed with a bladed screwdriver.. not an allen head screw.. Am I seeing this correctly , thank you !