Hydraulic problem

smwwoody · November 07, 2013, 07:14:47 PM

I have a problem on my feller buncher. When I try to raise the head it moves super slow. If you throttle it down and right back up it will then raise at normal speed. you can then raise and lower it as many times as you want without a problem. then if you open or close the gathering arms or the accumulator arms the head will go back to raising super slow. If you have a tree in it it will not raise at all. throttle it down and back up it will work normal again. I switched the pilot lines on the main valve body between the raise and tilt spools and no change in the problem so I think the pilot system is OK.

HELP

Woody

leot · November 07, 2013, 07:41:32 PM

change the filter first then check the oil pickup screen if you can

Kemper · November 07, 2013, 08:07:43 PM

Change hydrolic filters, also might want to change fuel filters also.

smwwoody · November 07, 2013, 08:30:23 PM

Just changed all filters yesterday. Put in new pilot and main hydraulic filters agian today

Southside · November 07, 2013, 09:09:16 PM

Woody - is there a priority valve that feeds that line? I had one in a 540 that was worn internally and would physically stick so I would loose hydraulic function, work the throttle or even shut the machine off and it would work just fine. Drove me nuts, I pulled the filters, sump screen, pulled the valve it self and according to the book the springs were OK. Well, I was going to pull the pump when I decided to remove the valve insides - problem instantly solved. Hope you get it fixed soon.

SPIKER · November 07, 2013, 09:59:32 PM

Quote from: Southside logger on November 07, 2013, 09:09:16 PM
Woody - is there a priority valve that feeds that line? I had one in a 540 that was worn internally and would physically stick so I would loose hydraulic function, work the throttle or even shut the machine off and it would work just fine. ... Well, I was going to pull the pump when I decided to remove the valve insides - problem instantly solved. Hope you get it fixed soon.

Above quote sounds like this could be a reasonable solution, seen similar on our drilling equipment.

Not familiar with the machine nore do I have any hyd/elec schematics to look at but a couple items to look at.

Check for a shuttle valve (similar to the priority valves) as well on a return or a cylinder check could also cause it.

Other items to look at (Pump Type) may have high/low flow conditions that could be getting sticky.

Last item to check is for a bit of gook.o-ring stuck in the pilot flow into the main spool that controls it.

Quick test to up/down reversing it does that change it ot does it only happen from a full down post (can't go lower) >?

good luck.

Mark

kiko · November 08, 2013, 12:38:19 AM

Woody, hard to tell from here but sounds like a sticking port relief . Swap the boom up and boom down port relief and see if changes. The port reliefs will be located in the spool section it self, just above where the pilot lines hook up.