3-Point Hitch 3 ph jumps when using remotes

[jimmysisson]

I have a 1993 Ford 2120 diesel with the EHSS hydraulic reverser. When I use the (single, factory) rear remote to open or close the grapple (long hoses), as I let go of the remote lever, the 3 point hitch jumps up maybe an inch then drops again. The jumping takes maybe 1/2 second, and it's kind of a shudder or jolt. I confess I don't know exactly how the 3ph is plumbed v. the remote, but this is a factory setup.
It's been doing this for eight years, and probably longer; that's when I bought it. No harm seems to come from it, but I've been wondering why it does that. Any ideas? Thanks
Jim

 

[Jerry/MT]

I think it's caused by a transient pressure spike as the valve shifts from high pressure actuator delivery circuit to the open center return circuit. If the three point hitch has no load on it, this pressure spike is probably strong enough transiently increase the pressure on the lift piston and can cause it to "jump". Does it jump with agood load on the three point? I think an orifice on the valve high pressure supply might reduce the magnitude of the spike.

 

[jimmysisson]

I think it's less the more load is on the 3 pt. by orifice, do you mean a restrictor in the "extend" line of the remote? I'd hate to restrict the speed of the remote lines, though I don't use them for anything like a wood splitter.
Does anyone else get this behavior?
Jim

 

[Leejohn]

Sound like your remote valve doen't have a load check in the valve. You might try, when opening or closing the grabber when it bottoms out just bump the lever the other way to unload some of the pressure. That might stop it.

 

[jimmysisson]

I've tried to feather the closing of the remote valve, but that doesn't seem to make any difference. Do you think a load check as you call it would be standard with the valve? I don't think anything's been changed in the hydraulics since new. I just wonder if anyone else has a rig that jumps this way.
Thanks, Jim

 

[jinman]

Jim, what looks like an inch may be much less right at the 3PH lift cylinder. I think you might have a small leak in the 3PH cylinder. The loader is the first in line, followed by the remotes, and finally the 3PH. My 3PH is completely bypassed when I use my remotes. If your 3ph lift cylinder leaks down a tiny bit, it could be correcting when pressure is restored on centering the remote. Of course, if you use full joystick motion on the loader, it should do the same thing. If it only does it for the remote and not when you use the loader, then it's a real mystery. I'd shut off the tractor with a full load on the 3PH raised up, then work the remote and see if the 3PH drops or if it drops by itself when the engine is shut off.

 

[jimmysisson]

Thanks Jim. Next time I'm out I'll try it. The 3ph will stay up with a 3-400 lb weight on it for a day or two so I'm not sure what would be leaking. Of course when I got it eight yrs ago it would stay up for a week or more. Still it's in better shape than I am some days!
Jim

 

[jimmysisson]

It only jumps when I use the remote, not with the loader.

 

[jinman]

Well, something is causing a spike to the HPL valve. One more thing to check is to disconnect your hoses to the remote and then operate the lever of the remote against a dead head so the relief valve lifts. In the process, if the 3PH still jumps, then I think there's a spike feeding back to the 3PH. If it doesn't move the 3PH, then ??? There is just nothing really that should effect the 3PH like that if the HPL valve is nulled and the 3PH cylinder is just holding pressure. There might be a sneak path for a pressure spike in the return side of the 3PH though. I guess one last question is if the 3PH jumps when it is all the way up, part way down, or almost all the way down? It's pretty baffling to me.