SCV stops retracting cylinder when lever is pushed all the way

[Magicman710]

I have a airblast sprayer that uses a double acting cylinder to turn the volute of the sprayer 180 degrees left and right.

When I hooked it up to my JD 5055E today, I noticed that the volute would only turn one way (cylinder extension), but would not turn the other way when the SVC lever was pushed forward. The tractor would strain and the hose would move a little, so I assumed there must be hydraulic fluid flowing.

I then discovered that if I only push the lever toward slightly, it would retract the cylinder. But if I pushed the lever all the way forward (right before the float detent), the cylinder would stop and the tractor would start straining again. I have to extend the cylinder again in order to retract it.

Summary:

- SCV extends cylinder no problem
- SCV only retracts cylinder when lever is slightly pushed forward. If pushed all the way forward, SVC stops retracting cylinder

I assume this is a SVC issue, as the cylinder works fine when tested with another tractor. I have a video demonstrating the problem that I can upload if necessary.

 

[arlen4720]

If you were saying this was happening if hooked to the loader valve, I would say the regen function is the problem. WHich SCV are you plugged into?

 

[Magicman710]

It is the rear SVC. Only one on the back of this tractor.

 

[xring100]

Did you try disconnecting and reconnecting both hoses. I had a similar issue on the lift arm circuit of my loader went up fine but didn't want to come down fast at all?

 

[xring100]

If the previous trick doesn't work swap the hoses and ports. Such the direction that was extending the cylinder now retracts it.
Then Report back

 

[the old grind]

On many (all?) JD's 5xxxs the rear SCVs worked by the joystick have float (fwd) or regen (hard right) functions on the stick positions/spools for loader use. Not sure which one would put your system into stall/bypass but regen seems more likely than float & I'd bet you're using S x S stick moves with the sprayer. Does it bog at full swing to the one side? IIRC regen does the same at the far end of a full FEL dump.

The joystick doesn't control the amout of cyl travel, only direction and speed, nothing 'proportional' about how far you push it like some video game controllers (Nintendo) or sophisticated RC cars/planes.

If this issue just popped up there could be something amiss with a spoool or linkage. If nothing is wrong and it's only a discovery on a new mount-up you'll just have to get a feel for what to expect when approaching the extreme of whichever stick position.

 

[J_J]

If your spool is set to push fluid into a cyl and the engine strains, then it is pushing against a blockage.

Maybe a QD problem. Reset the QD's or replace.

 

[Magicman710]

Well I went out and played with it again a little while ago, and actually got it to work. The cylinder would fully retract and extend no matter how far I push the lever, though it would extend a little faster than it would retract. I then switched the hoses on the couplers, and the issue started again. Cylinder extends no problem, but will want to stop if I push the lever to the max. I switched them back and its doing the same thing...

Here's a video for a visual (and audio) demonstration. Notice whenever the volute stops moving is when I'm pushing the lever the furthest.

https://www.youtube.com/watch?v=DoTAGU1dX00

 

[the old grind]

.... The cylinder would fully retract and extend no matter how far I push the lever, though it would extend a little faster than it would retract. I then switched the hoses on the couplers, and the issue started again. Cylinder extends no problem, but will want to stop if I push the lever to the max. I switched them back and its doing the same thing...

Here's a video for a visual (and audio) demonstration. Notice whenever the volute stops moving is when I'm pushing the lever the furthest.

https://www.youtube.com/watch?v=DoTAGU1dX00

Cyl volume and flow to actuate it affects action velocity, so faster retracting than extending for the most part. At max in one the one direction (stick right) and if in regen position the return oil is directed to the other side of the piston. If dumping a bucket in regen mode (bucket extension) the weight of the load doesn't have to rely on pump flow alone to actuate, and it dumps fast. (Can't exert down-pressure in regen detented position on my Deere ... or the NH.)

In the same stick position (rt max/regen), if the spray head is rotating upward gravity is not assisting the cyl's action. (cyl 'bypassing' at spool vs pump flow?) I wouldn't expect it to move freely (at max) until the sprayer rotates to over-center position. This (working smoothly) still seems a matter of how far the stick is worked in the direction where the regen function is activated.

What I mean is, max in one direction works (left stick), but don't expect the same action at the same velocity for the same movement of the stick both ways ... nothing symmetrical L to R there, and don't just snap it full right into regen. Partial-stick in the iffy direction must be why/when it worked ok, and that seems to be what the video shows but hand on the stick isn't in there to vet or discredit what I'm getting at.

I apologize if I'm that far off base, but this does look like a new install and a new experience with the sprayer, and only a learning curve (joystick) to contend with.

 

[arlen4720]

Cyl volume and flow to actuate it affects action velocity, so faster retracting than extending for the most part. At max in one the one direction (stick right) and if in regen position the return oil is directed to the other side of the piston. If dumping a bucket in regen mode (bucket extension) the weight of the load doesn't have to rely on pump flow alone to actuate, and it dumps fast. (Can't exert down-pressure in regen detented position on my Deere ... or the NH.)

In the same stick position (rt max/regen), if the spray head is rotating upward gravity is not assisting the cyl's action. (cyl 'bypassing' at spool vs pump flow?) I wouldn't expect it to move freely (at max) until the sprayer rotates to over-center position. This (working smoothly) still seems a matter of how far the stick is worked in the direction where the regen function is activated.

What I mean is, max in one direction works (left stick), but don't expect the same action at the same velocity for the same movement of the stick both ways ... nothing symmetrical L to R there, and don't just snap it full right into regen. Partial-stick in the iffy direction must be why/when it worked ok, and that seems to be what the video shows but hand on the stick isn't in there to vet or discredit what I'm getting at.

I apologize if I'm that far off base, but this does look like a new install and a new experience with the sprayer, and only a learning curve (joystick) to contend with.

He's not using the joystick