Aaargh! 3-pt hitch not lifting any weight.

[project_X]

As you may have seen, I have added a set of rear remotes to my 1602D yanmar and everything has been tested; loader, 3pt hitch and remotes without any problems.

Symptoms:
Today, I was finally getting to moving some earth with my box blade, everything worked well raised/lower 3pt hitch on multiple passes. I used the loader and my toplink cylinder, no problems. All of a sudden my 3 pt hich would not lift my box blade. By setting the lift control to the highest up position, and moving the toplink out and in, I was able to get the blade off the ground and back to the shed.

I did not touch the control knob at all. I did check it after getting back to the shed, and it didn't have any effect on the raising.....

I removed the blade, lift would work with nothing on it.
I stood on the lift (180lbs on the lift arms), at 1500rpm they would hold position but not go up, at 2000rpm+ they would lift me.

Also standing on the lift, if I set the lift position to a high position and lowered the loader, it would raise the lift. using the toplink had no effect.
I checked the pressure into the IN port 3pt block, and it was 2000psi+ at 2000rpm or so.

The loader was able to lift the front of the tractor off the ground in the down position.

I then removed the loader from the circuit, it would not lift me unless it was at higher rpm.

I then removed the rear remotes from the circuit, so the only thing in the circuit is the 3pt hitch.
I checked the fluid level, it was good.
I assume the filters and pump are ok, if the loader and toplink cylinder can still
lift the tractor....

Possibilities:
Relief valve of 3pt hitch is not functioning properly (where do I connect a gauge to see the pressure?
Control Valve
Lift Cylinder
Anything else?

Here is a picture of the block under the seat

Any ideas? What should I try next?

Thanks,
Rob

 

[J_J]

The knob under the seat is there to set the descent rate. If it is locked down, the 3pt cyl should not move. If it is binding, it may not move or move very little. You could take the assembly out and clean it and look for rust, debris, etc.

You can install the gage anywhere from the pump to the 3pt.

If you want to monitor the pressure in your tractor hyd system, install the gage in the IN port of the FEL valve. Then anytime you are using the hyd's, the pressure will be reflected on the gage.

Keep in mind, that pressure is only built up when a cyl or motor is doing work. Some work requires very little pressure.

If you max out the 3pt, or pull lever up fully, the 3pt relief valve should come on , and you can read the pressure on the gage. You can also remove the 3pt relief valve and inspect and clean, etc. It may be fixed or adjustable, just don't know.

Your manual might help some with the operation of the hyd system.

 

[project_X]

JJ,

I will mount a gauge on the in of the fel tomorrow to see the pressure.

I move the knob back and forth, but will clean it tomorrow as well.

What do you think might cause the 3pt to raise when I was lowering the FEL, but not move when it the loader was raising or bypassed? BTW: my loader is plumbed without a PB port (like a lot of the Yanmars).

Would a relief valve just stop working?

 

[J_J]

Someone answer this question. If I raise the 3pt half up, and lock down the descent valve, it is not supposed to descend any lower, but can it still raise up with the 3pt lever, or does it close off the 3pt cyl?

From my understanding, the 3pt valve lets fluid into the cyl through a small port, and this port is where the descent valve is located. With the knob open, the fluid flows in and out the 3pt cyl via this port/orifice. There is also supposed to be a safety valve in the 3pt also.

Anybody have a better explanation, I would like to hear it.

Relief valve can quit anytime.

If your 3pt lever is not in neutral, it might raise.

If the 3pt lever is raised to much, the 3pt relief valve will relieve continuously.

Even if the valve is relieving, you might have some action, as the relief valve is relieving at about 2500 psi or whatever your system is set for. The relief valve can not get rid of the volume of fluid as fast as the pump is pumping.

 

[project_X]

Update:

I decided to change all my fluids, check screen (it was perfectly clean) and changed filter.

I remove the 3pt cylinder and all the seals look good. I cleaned the control valve with naptha, but everything looked clean.

I put everything back together. Filled with fluid and started everything up.

The lift functions the same, it can handle very little weight. If I stand on the lift arms, it will not raise me up (180lbs) until I increase the rpm. It will hold me if I stop it from raising.

Without the loader in the circuit, I put a pressure gauge on the output of the pump.
Pressure readings:
No valves engaged 0psi
remote valve (nothing connected) 2100psi
remote moving toplink out 450psi
remote moving toplink in 750psi
three pt hitch raising(nothing on the arms) 200psi
three pt hitch not raising(me on the arms 1500 rpm) 200psi
three pt hitch raising (2000 rpm, me on the arms) 450psi

What should I try next?

 

[project_X]

the loader lifts with me standing on it.

I shimmed the relief valve to make it stronger, but it didn't have any effect.

I tested the flow, and my guesstimate, is that it was flowing about 5gpm (more than a gallon in 15 secs) at 1500 rpm.

I guess I will remove the rest of the relief valve to see if something is caught in it?

Any other ideas?

 

[284 International]

J_J knows vastly more about this than me.

It seems like the fluid is bypassing the lift cylinder, but at high flow volume (High engine RPM) there is sufficient flow to "back up" the system, and allow the cylinder to lift. What confuses me is that you say it will hold weight once it has raised. I would expect, in my ignorance, that if there was a leaking relief valve that the system would immediately bleed down.

I read in your original build thread that you have the plumbing like this:

pump->loader valve in->loader valve out->plug diverts flow out of 3ph body (before it enters the valve)->
new valve in -> new valve out-> reservoir
----------------> new valve pb-> 3ph->reservoir.

When you say that you have removed the loader from the circuit, does that mean it runs pump to plug diverter, and the same from there out? What if you put it back to factory configuration on the plumbing? Perhaps that may isolate where the problem is. I'm pretty ignorant about this, but it "feels" like the problem is related to how the fluid is being diverted.

Also, PM sent.

 

[project_X]

J_J knows vastly more about this than me.

It seems like the fluid is bypassing the lift cylinder, but at high flow volume (High engine RPM) there is sufficient flow to "back up" the system, and allow the cylinder to lift. What confuses me is that you say it will hold weight once it has raised. I would expect, in my ignorance, that if there was a leaking relief valve that the system would immediately bleed down.

I read in your original build thread that you have the plumbing like this:

pump->loader valve in->loader valve out->plug diverts flow out of 3ph body (before it enters the valve)->
new valve in -> new valve out-> reservoir
----------------> new valve pb-> 3ph->reservoir.

When you say that you have removed the loader from the circuit, does that mean it runs pump to plug diverter, and the same from there out? What if you put it back to factory configuration on the plumbing? Perhaps that may isolate where the problem is. I'm pretty ignorant about this, but it "feels" like the problem is related to how the fluid is being diverted.

Also, PM sent.

I put it back to the original state, but no change. I then put it back to the state with loader, remotes and 3pt valve, to have additional test points.

 

[project_X]

I removed everything from the relief valve, and it looks like there are only a few of parts (a lot less than the manual I have for a 226D.

lid
shims
spring
plunger
ball

everything looked fine.
but it still has the same problem.

is there another relief in the yanmar?

 

[Leejohn]

There is one in the 3pt valve. Sounds like it is stuck open.