Aaargh! 3-pt hitch not lifting any weight.

[Leejohn]

Here is some good reading on your 3pt. http://www.tractorbynet.com/forums/...y-lseries-3pt-hitch-fixed-18.html#post2472447

There is 2 or 3 O rings under the valve, one of them might of blew out.

 

[project_X]

Here is some good reading on your 3pt. http://www.tractorbynet.com/forums/...y-lseries-3pt-hitch-fixed-18.html#post2472447

There is 2 or 3 O rings under the valve, one of them might of blew out.

that makes sense, I just need to get a nice diagram of my valve, so that I can put it together after I get it apart.

 

[Leejohn]

You might try this. Go to the John deere web site and look up the parts manual for a John Deere 750 and see if it looks like your valve. That is a 20HP, but don't order parts from there because it might not be the right match
for your tractor.

 

[project_X]

You might try this. Go to the John deere web site and look up the parts manual for a John Deere 750 and see if it looks like your valve. That is a 20HP, but don't order parts from there because it might not be the right match
for your tractor.

thanks, i tired that yesterday, no luck.

 

[284 International]

J_J, I tried closing the lock valve on two of my Yanmars and then attempting to raise the three point. Both immediately went into bypass. This is true whether the implements were up, down, or in between.

I'm really too ignorant about this subject to be of much help, but I'm interested in learning. It seems to me that the flow of the pump is going to be constant at a given RPM. It is capable of developing reasonable working pressure, since he can get pressures of 2000 psi or so on his gauge.

When he is trying to operate his 3 point lift, he can only get pressures of about 450 psi, but only at maximum pump RPM/volume. Anything over around 450 psi, by my reading, won't let the system lift the load. In my limited understanding of how these things work, that seems to imply that there is a restriction to flow in a bypassing system that is restricting the flow of fluid to 450 psi at, say, 4 gpm, thus pressurizing the lift cylinder to that as well.

If that is true, the choice seems to be whether there is a stuck or weak bypass valve, or if the control valve itself is passing fluid.

Is that correct?

A tangential thread-jacking question: Say the lift piston seals are leaking fluid. Where does that leaked fluid go? Is there a return line on the non-pressurized side of the piston to the reservoir? Does it escape out the vent when sufficiently accumulated?

 

[project_X]

here is a diagram of my valve assembly

any place i should start?

 

[Leejohn]

I found a valve that is almost like yours and it was on a JD 790. I would start at the 3 o rings then to the poppet under cap #7 and #10. That valve under 7 goes all the way to plug 10. If it was me I would take the hole valve apart now that you have the brake down. If # 10 is a hex plug then you should look at the JD790 parts list, also you can read the parts names. I'm sure you checked lever linkage of anything loose or broken right?

 

[J_J]

284 International,

GPM's , only dictate the speed of operation. The resistance to the hyd fluid is what builds pressure, such as when you try and lift a 1000 lb load, or you raise the 3pt lever and cause the 3pt cyl to fully extend. If the relief doesn't come on, then the cyl is probably leaking. When the cyl leaks, it leaks into the sump. If you can't build pressure by raising the 3pt lever, something is leaking. If you can make the 3pt go into relief, then you should have enough pressure to operate the lift.

I would first remove the components for the lock down knob and inspect and clean it.

The 3pt valve or the cyl could be leaking.

I believe you verified about the lock down/ descent knob. If closed, no fluid in or out.

 

[284 International]

I'm not trying to be argumentative, I just don't understand where the fluid could be going.

Is it correct to say that A) If the lock valve is closed, the fluid isn't going through there, and B) If the implement will stay raised, it isn't leaking past the cylinder?

 

[project_X]

I found a valve that is almost like yours and it was on a JD 790. I would start at the 3 o rings then to the poppet under cap #7 and #10. That valve under 7 goes all the way to plug 10. If it was me I would take the hole valve apart now that you have the brake down. If # 10 is a hex plug then you should look at the JD790 parts list, also you can read the parts names. I'm sure you checked lever linkage of anything loose or broken right?

i've inspected the linkage, and don't see anything that looks out of place or broken. the lift does lift minimal weight, if I get the volume of flow high enough. at low volume it won't lift, but will hold position.