Fabtek 4 roller

[logloper]

The feed rollers are not maintaining pressure against the tree when rolling. They will close when you hit "close all" and they do have pressure when you keep bumping the "rollers close" button. My last Fabtek, the rollers would sqeeze the tree any time you hit the rollers. Any ideas?

[bushmechanic]

Maybe you have a bad seal kit in your roller grip cylinder. Use a heat gun and see if any certain place on the barrel is hotter than the rest.

[logloper]

I can try that. But, if the rollers are open and I hit the "roll" switch the rollers do not close. I believe any time you hit the "roll" switch, pressure to close the rollers should be applied automatically. I could see a seal kit if they wouldn't maintain pressure, but they aren't even closing in synch with the "roll" function.

[wannaergo]

Almost sounds like an electrical problem. If the switch is running the rollers it should be telling them to close as well.

[deastman]

Are the older Fabteks supposed to apply pressure when the rollers are activated?  Mine is a '99 model and it has never done that. I have to activate the delimb function or hold the rollers close function to keep pressure on the rollers.  Guess I'll have to take a look and see if something happened or someone changed mine before I got it.

[Corley5]

Mine's a '99 and the rollers close when I hit the feed button.

[bushmechanic]

Sorry logloper your confusing me a little.You first said that the feed rollers are "not" maintaining pressure and in your next post you said that you could see a seal kit if they wouldn't maintain pressure. Do the rollers spin out on the stick when feeding? I think that if it's not closing when you hit the feed button that may be a setting in the computer. I know that the Timberjack/ Deere will do that.

[deastman]

Ok,  thanks Corley5, I'll take a look and see if I can find out why mine doesn't work that way

[logloper]

Sorry for any confusion. The rollers do not apply pressure when told to" roll". When closed already, they do not apply additional pressure when told to "roll". I think when told to "roll", they should automatically apply X amount of pressure. Right now when you tell it to "roll" the rollers do not keep closing to follow the taper of the log. You have to tell it manually.

[bushmechanic]

Ahh now I gotcha. I had feed problems this week with a Timberjack 745 head and it kept spinning out on the tree. When I found the problem it was a small piece of metal catching in the low pressure relief for the close rollers. You need to install a pressure gauge on that circuit and grip a big standing tree and feed down so the head will stall and you can get a relief pressure reading. Usually the computer controls any of the functions that assist with processing. You may need to access the computer to reset it. It's been a good 12 to 14 years since I worked on a Fabtek head but if I remember correctly the access code was the phone number to the old Fabtek factory, sorry can't remember it. You better be confident with your computer skills if you go in there because you can screw it up real bad real quick. A service manual would be ideal right about now!

[logloper]

So I went ahead and repacked the cylinder that opens and closes the "rollers". No difference. Also had the accumulator charged. No difference.  The rollers wont stay tight against a tree while cutting either. This allows the tree to come down on the saw bar and pinch it while cutting. Is there a check valve somewhere? I did read in the book that a jumper has to be soldered between 2 terminals in the computer box in order to make the rollers close when they are told to roll. But, I need to figure out why the pressure is bleeding off in the first place. Advice would be appreciated.

[Corley5]

Sounds like the problem is in the valve.

[logloper]

Agreed, I was thinking of switching the lines from the knives to the valve to the rollers, and the roller lines to the valve that goes to the knives. That should show if the valve is bad. I think. What do you think?

[bushmechanic]

You can do that but remember you need to control that other valve with the electrics for the roller close and the pressure settings may not be the same on the knife functions. What kind of valve controls the function? I mean is it a solenoid slid on a shaft or is it bolted on? If you have a cartridge valve ( one with a nut on the shaft) you can unscrew it and the shaft is the valve. I have seen the o-rings and backup rings go on those. I remember that on the Fabtek we had trouble with a aluminum valve block splitting open and the replacement was a steel one because the origional one couldn't take the pressure.

[logloper]

I will look at what kind of valve it is and check seals . Thanks.

[c greenham]

Hi Logloper,

Did you every find out what the issue was for rollers not maintaining pressure?