646 extension boom

[Firewoodjoe]

The darn extension boom quite coming back in. It's electronic over Hydraulic. Solenoid on each end of the spool. On/off solenoids. I've already determined it's not the joystick micro switch. What's weird to me is you can't get it to come back in for nothing. Even pushing on the ground but if you set it down in the dray and grab the bar with the grapple that's for transport. And set the boom down then it will just push back in. I switched the hoses so we could at least just have it pull in, at least until I ordered solenoids. Well that won't work. It labors hard pulling it back in and then will just slid back out trying to pick up a log. Like the hoses are right off the cylinder!  It acts like a valve is stuck somewhere. I'm going to swap the solenoids to see if that makes it reverse positions and work. Any ideas of what's going on would be appreciated. 

[barbender]

Is that a single stage, or 2 stage extension? Or another way to ask, does it use just an extension cylinder, or does it have a boom chain as well?

[Gary_C]

My guess would be there are some pieces of O rings floating around in that valve. Find out which valve controls that function and pull the spools and clean out the pieces and put new O rings on the spool.

[Southside]

Does that have the check valve, for lack of the correct term, on the cylinder that requires pressure before it will allow the cylinder to move? It's a block that is welded to the cylinder the hose goes into with a cartridge valve on it.  I had a cartridge on one of those go bad on my Lull and it acted much like you describe.  

[Firewoodjoe]

Ok. I just ran it myself. Cold it works dozens and dozens of times. I couldn't get it to stop. So I'm assuming the solenoids are ok. Maybe it's the infamous shuttle valve problem. I always liked my lever controls lol  he's going to go run it and pay close attention to time and functions he's running as to when it stops working. Thanks for the quick responses. 

[Firewoodjoe]

Sticking valve. I've put more money in this forwarder than anything I've ever owned. Be like new someday🤦‍♂️