Unless you hit another lever. It will lift right up at idle if you hit the Dipper, bucket or swing peddles. But won't lift even at full throttle if you don't .
Did you get your issue resolved with the backhoe? I've got a 780d doing the same thing. Housekeeping note: I moved this post, and the next two, from a different thread, so that this thread can be specific to the 780. ~Digger242j
Dave, you mean your boom won't lift unless you activate another function? What's the history of this machine? and the history of the problem? I'd pull that spool out of the valve body and look through there with some light shining through the other end. First, check to see that the spool moves the same distance in and out as the one on either side of it. Then check the bottom end bits under the cover at the bottom of the spool (#8 in the diagram), then try the spool again for distance compared to the neighbors. Then remove 2-7 and lift the spool out of the valve body. If it doesn't come out easily, you have your answer, sorry, don't force it.
Hi Delmar, I bought the machine a little over a year ago. It sit around along time. I repacked most hoe cylinders. Alot of hoses and such. It just won't lift the boom unless you have the boom lever pulled back and you either hit a swing peddles or move the Dipper or but let lever slightly. I saw one post that said it was the secondary shuttle orings so thought I might check that in the morning.
Welcome to HEF @780Dave ! You're on to it!
That rings a bell, good thing somebody remembers this stuff. Please let us know what you find.
That backhoe valve is the same valve that was in the 1150B,C and D there are what we call primary and secondary shuttles that controls the pressure in each section. There are allen head screws in the back and bottom of valve sections. They have neoprem orings that go bad.
No solution, but similar problem. I had a 780C years ago that all of a sudden would not swing left unless you activated another motion. Local hydraulic shop had all valve banks out and cleaned everything and replaced all seals. He was a good friend so I was there for the whole job. Ran the same after all of that work. Never did get it fixed and sold it for a Case 590. It was a beast and could load a dump truck in a hurry. Steve
Ok, finally located enough parts to resealing valve stack. Several bad orings in the shuttle valves. Put it back together and in, started it and it works fine so far. Super glad it worked cause it's a tough job taking it in and out. hope some are easier than this one.