Joystick Controls All or Nothing

[Scott McFadden]

I’m working on a Linkbelt 130 X2 excavator (13005NJHEX1288) The machine tracks fine, but the boom down joystick control doesn't work, but all of a sudden, randomly will. When the function does work the boom goes down at full speed/force. You can’t ease the control. All joystick controls (excavator swing, bucket curl, etc.) do the same thing, but the boom down function is by far the worse.

Pumps 1 and 2 reading 350psi on the screen.

I tested the outlet of the charge pump assembly and it was reading 700PSI. I tested after the hydraulic filter just before the 4 bank solenoid block. It also was at 700PSI. Both hydraulic filters did not have silver or debris in them.

Any suggestions? Thank you.

 

[8V71]

I have scene a similar issue with a Deere 250G. You had to move the joystick almost all the way forward then the boom would take off, coming down rapidly. The issue there turned out to be a slightly tweaked boom spool in control valve, causing the pilot oil pressure to have to build up on on the spool before shifting it.
Don’t think that would apply to the issue you are having with all the functions doing it. I assume the joysticks are pilot/hyd and not PWM control.
And why it’s affecting both joysticks and not the tracking pilot valves. I would at least check the pilot oil pressure to the spools of the affected functions and compare them with the tracking spool pilot pressure.
I typically do an in-line tee test as well as a dead head test.

 

[Vetech63]

I'm wondering if your machine has the debris screened fitting at the inlets of each manipulator/valve. They get missed all the time. I know a lot of Japanese machines use them.

 

[Scott McFadden]

I'm wondering if your machine has the debris screened fitting at the inlets of each manipulator/valve. They get missed all the time. I know a lot of Japanese machines use them.

where are these screens? Do you mean at the Joysticks? They are hydraulically controlled and not PWM.

 

[Scott McFadden]

I have scene a similar issue with a Deere 250G. You had to move the joystick almost all the way forward then the boom would take off, coming down rapidly. The issue there turned out to be a slightly tweaked boom spool in control valve, causing the pilot oil pressure to have to build up on on the spool before shifting it.
Don’t think that would apply to the issue you are having with all the functions doing it. I assume the joysticks are pilot/hyd and not PWM control.
And why it’s affecting both joysticks and not the tracking pilot valves. I would at least check the pilot oil pressure to the spools of the affected functions and compare them with the tracking spool pilot pressure.
I typically do an in-line tee test as well as a dead head test.

I did check pilot pressure going to the boom down spool and it was 0psi while I was moving the joystick, but would eventually all of a sudden shoot up to 600psi and the boom would drop suddenly and quickly.

I also tested at the output of the 4 bank of solenoids and it is 600 psi whenever the joysticks are being moved and 0psi when the joysticks aren’t being moved. So i know that works properly.

 

[8V71]

The pilot pressure should increase proportionally with the movement of the joystick . And you said all the other functions are doing this? You might remove the boot on the joystick and check the plate to plunger clearance and how the plungers seem to function (not sticking or out of sorts in any way). You could also try moving some pilot lines around to see if the issue moves just make sure you don’t lose track of where they go.If the machine has a pattern changer that would be an easy way to try that

 

[Scott McFadden]

Th

I have scene a similar issue with a Deere 250G. You had to move the joystick almost all the way forward then the boom would take off, coming down rapidly. The issue there turned out to be a slightly tweaked boom spool in control valve, causing the pilot oil pressure to have to build up on on the spool before shifting it.
Don’t think that would apply to the issue you are having with all the functions doing it. I assume the joysticks are pilot/hyd and not PWM control.
And why it’s affecting both joysticks and not the tracking pilot valves. I would at least check the pilot oil pressure to the spools of the affected functions and compare them with the tracking spool pilot pressure.
I typically do an in-line tee test as well as a dead head test.

this does have deere and cat controls.

when I switch controls the biggest problem usually stays with the right stick pushing it forward (boom down/boom out). But the problem seems to be intermittent. Sometimes the left stick acts up more, sometimes less when I change controls.

i checked pressure at the bottom port of the 4 bank solenoids. This is supposed to feed a “PT adapter” which then provides the pressure feed to the joysticks. This had 600psi whenever the safety lever was down. I still need to confirm that “PT adapter” is good. I’m not sure where it is. This will verify I have good pressure going to the joysticks right?

After the joysticks at the cushion valve/deere and cat control switch I tested the boom down line. As I was feathering boom down the gauge read zero. As the book suddenly dropped the gauge shot up to 300-400 psi. No proportional pressure increase.

should I try swapping joysticks with another machine? Or is there another valve I’m missing? Or could this PT adapter be my problem? Or the screen mentioned earlier?

 

[Scott McFadden]

The pilot pressure should increase proportionally with the movement of the joystick . And you said all the other functions are doing this? You might remove the boot on the joystick and check the plate to plunger clearance and how the plungers seem to function (not sticking or out of sorts in any way). You could also try moving some pilot lines around to see if the issue moves just make sure you don’t lose track of where they go.If the machine has a pattern changer that would be an easy way to try that

Sorry, I also do have the right stick ripped apart. The hydraulic lines going into the bottom of the stick are covered by a plastic tube. I haven’t figured out how to access them yet or see the plungers.

 

[Scott McFadden]

I’m working on a Linkbelt 130 X2 excavator (13005NJHEX1288) The machine tracks fine, but the boom down joystick control doesn't work, but all of a sudden, randomly will. When the function does work the boom goes down at full speed/force. You can’t ease the control. All joystick controls (excavator swing, bucket curl, etc.) do the same thing, but the boom down function is by far the worse.

Pumps 1 and 2 reading 350psi on the screen.

I tested the outlet of the charge pump assembly and it was reading 700PSI. I tested after the hydraulic filter just before the 4 bank solenoid block. It also was at 700PSI. Both hydraulic filters did not have silver or debris in them.

Any suggestions? Thank you.

Just wanted to give everyone an update. I tested the pilot pressure going into the joysticks and got 600PSI when the safety lever is in work mode and 0 PSI when the safety is on. I then tested the boom down output from the joysticks and was getting 0 PSI while feathering the controls down, but the pressure would spike as the boom suddenly dropped. I swapped joysticks with another Linkbelt I had in the shop for repairs and that fixed the problem.

The customer opted to blow out the ports of the joystick to see if that would fix the problem. I reinstalled the joysticks and they seem to be working okay so far.

 

[antpoo]

I’m having issue not exactly same. But no pressure in my forward drive pilot plunger, The rest are fine except left turn is slow. I’m guessing it’s blocked orifice that is the cause .