I have a 2001 JLG 2646 E2 electric scissor lift serial 0200094173. Has 211 hours of run time total so it is really in good shape. It has brand new batteries (2 days old). It lifts up and down perfect with plenty of power, the steering moves perfect, the brake cylinder retracts fine. However,when you try to drive forward or backward it hesitates. Usually it hesitates for 5 to 10 seconds before it then moves. The pump motor is whining away as normal, but it just does not move. When it does finally move it usually gives a slight jerk and then rolls on. If it has been run in the drive mode for awhile and then you stop it for a few seconds, it seems to drive on again with a significantly lesser amount of hesitation (maybe 1-2 seconds). However, if you let it sit and do not drive it for about 3-5 minutes then it again hesitates in moving for 5 to 10 seconds. Sometimes longer. The pump motor whines but the lift does not roll forward. Almost like it is "slipping" but then suddenly grabs after this long period of time. Sometimes it never grabs and slips until you turn it off, but mostly it grabs after 5-10 seconds.
At first, I found that it would drive forward or reverse right off if I pressed the right turn or left turn button at the same time. However, this then stopped helping and that trick no longer works. I have been at a loss to what is wrong here. Here is what I have done so far:
1) I checked the solenoids on the drive forward and drive reverse. Voltage was about 20 V. This seemed to be a little low as I thought it might be 24V but the solenoids worked well and had correct resistance. I thne bought brand new batteries but still no improvement.
2) I then bypassed the solenoid control by disconnecting the wiring and hardwiring a separate 24V source to energize the solenoids. This way I took the joystick/controller out of the picture. Same symptoms. Hesitated driving.
3) I then removed the entire forward/reverse solenoid spool valve (Rexroth ManneMann valve 4WE6E60) and brought it to my clean bench where I took it apart. I checked to make sure that the spool moved OK when the solenoids were energized. The spool moved back and forth fine. (I did notice that the spool diameter and the bore of the housing had about .002 clearance and there were no O rings on it. I am not an expert on spool valves so maybe this is fine, but I would have thought it would have been a tighter clearance. However, there was not signs of wear or galling on the spool OD or bore ID so maybe this is how it is supposed to be?) Everything fine in the spool, no gunk, perfectly clean.
4) I put the entire thing back together and remounted on the JLG lift. When I tried it, same thing. Lift hesitated just like before.
5) I then checked the TOW valve to make sure it was closed. It is tight. If you unscrew it the lift does not drive at all which is how it should be. I am not sure if there is any leakage or this TOW valve is a problem but from what I can tell it seems fine. I took the valve out and inspected it and it looked brand new and seemed to seat fine.
6) I checked the drive in both high and low speed. The lift does the same thing (hesitates) in both the slow and high speed settings.
7) I have just got a gauge to measure the pressure from the MP port. Will do this tomorrow. However, since everything else works fine and strong, I don't think this is an issue with the pressure.
8) I thought about the drive motors themselves having problems. However when it does move it moves strong. Also, the machine only has 211 hours on it. I would not think the motors (or both motors at the same time) would be bad but I have not disproved this yet.
9) Has plenty of fluid, filter is brand new, no clogs in air vent, hoses are fine.
10) I am not sure when this drive hesitation started as we had been using it mostly for up/down. I did move the machine recently with my Lull and it got shook around slightly but nothing drastic.
Any suggestions would be greatly appreciated. I have all the JLG on line manuals but they do very little to help with this particular problem. I had tried calling JLG but they would not talk to me as I do not have an account. I tried to get an account only to find that I would need to be a dealer and sell a certain number of machines to qualify. (I am a builder and not a JLG sales store) I tried calling JLG service but no one can get to me for quite a long time and when they do, travel time and costs get pretty prohibitive unless I was to ship the machine to them. I do not have a trailer or truck big enough to move this machine. I would really like to be able to fix this on my own as I enjoy working on these machines. Thanks for any suggestions!
At first, I found that it would drive forward or reverse right off if I pressed the right turn or left turn button at the same time. However, this then stopped helping and that trick no longer works. I have been at a loss to what is wrong here. Here is what I have done so far:
1) I checked the solenoids on the drive forward and drive reverse. Voltage was about 20 V. This seemed to be a little low as I thought it might be 24V but the solenoids worked well and had correct resistance. I thne bought brand new batteries but still no improvement.
2) I then bypassed the solenoid control by disconnecting the wiring and hardwiring a separate 24V source to energize the solenoids. This way I took the joystick/controller out of the picture. Same symptoms. Hesitated driving.
3) I then removed the entire forward/reverse solenoid spool valve (Rexroth ManneMann valve 4WE6E60) and brought it to my clean bench where I took it apart. I checked to make sure that the spool moved OK when the solenoids were energized. The spool moved back and forth fine. (I did notice that the spool diameter and the bore of the housing had about .002 clearance and there were no O rings on it. I am not an expert on spool valves so maybe this is fine, but I would have thought it would have been a tighter clearance. However, there was not signs of wear or galling on the spool OD or bore ID so maybe this is how it is supposed to be?) Everything fine in the spool, no gunk, perfectly clean.
4) I put the entire thing back together and remounted on the JLG lift. When I tried it, same thing. Lift hesitated just like before.
5) I then checked the TOW valve to make sure it was closed. It is tight. If you unscrew it the lift does not drive at all which is how it should be. I am not sure if there is any leakage or this TOW valve is a problem but from what I can tell it seems fine. I took the valve out and inspected it and it looked brand new and seemed to seat fine.
6) I checked the drive in both high and low speed. The lift does the same thing (hesitates) in both the slow and high speed settings.
7) I have just got a gauge to measure the pressure from the MP port. Will do this tomorrow. However, since everything else works fine and strong, I don't think this is an issue with the pressure.
8) I thought about the drive motors themselves having problems. However when it does move it moves strong. Also, the machine only has 211 hours on it. I would not think the motors (or both motors at the same time) would be bad but I have not disproved this yet.
9) Has plenty of fluid, filter is brand new, no clogs in air vent, hoses are fine.
10) I am not sure when this drive hesitation started as we had been using it mostly for up/down. I did move the machine recently with my Lull and it got shook around slightly but nothing drastic.
Any suggestions would be greatly appreciated. I have all the JLG on line manuals but they do very little to help with this particular problem. I had tried calling JLG but they would not talk to me as I do not have an account. I tried to get an account only to find that I would need to be a dealer and sell a certain number of machines to qualify. (I am a builder and not a JLG sales store) I tried calling JLG service but no one can get to me for quite a long time and when they do, travel time and costs get pretty prohibitive unless I was to ship the machine to them. I do not have a trailer or truck big enough to move this machine. I would really like to be able to fix this on my own as I enjoy working on these machines. Thanks for any suggestions!
JLG 2646 hesitates when moving forward or backward
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