weird issue with fel valve

[emanaresi]

I have a kubota l4610 with an la852 fel. I just bought it and a problem has become apparent since then.

When I pull the lever to raise the fel, it raises fine, slowly. But if I pull the lever past about 1/3 position to full lift, the loader just stops. If I move the lever back to slow lift, it starts going up again. I have checked all of the quick disconnects, I have completely disassembled and cleaned the hydraulic valve, I just can't ind any issues.

Its not that big a deal to just replace the valve, but I can't even wrap my head around what the issue could be. Please help me out.

 

[J_J]

If you install a hyd gage in a tee connected to the IN port, the pressure readings should help you troubleshoot the hyd system.

 

[Leejohn]

Look where the pressure line is hooked. It's the hyd block and there might be a slot that you can turn to shut the loader off and on. Make sure it has not got turned.

 

[emanaresi]

I checked the hydraulic block, it is turned correctly.

JJ, how much pressure does the gauge need to read?

 

[J_J]

Most tractor hyd pressure are about 2500 to 3000 psi, so a 3000 psi gage would work fine.

If you need a gage, look here.

Surplus Center - 3000 PSI 2.5" LF LM GAUGE

or Northern tools,

or TSC store.

 

[Farmerford]

JJ is correct about testing the pressure, but your problems might be something else. The answers to these questions my help isolate the issue.

1. When the FEL boom rise slows at 1/3 pull of the lever, does the rise stop suddenly or does it just get slower gradually as you pull the lever past the 1/3 position?
2. To return to slow rise after the booms stop, is it sufficient to just return the lever to the 1/3 position or do you have to return the lever all the way to neutral first and then return to 1/3 open?
2. Does the same thing happen when you lower the booms?
3. Does the same thing happen on the curl and dump?

 

[emanaresi]

1- It seems pretty abrupt, I would have to check very carefully to be sure.

2- If you just move the lever back to the 1/3ish position it starts going up again. You don't have to return to neutral

3. It does not happen when lowering the boom (I think). It is possible that it does but I didn't notice because if you go all of the way to lower, it goes into float and lowers on its own. But I don't think it does it while lowering.

4. it works fine in curl and dump.

What is your line of reasoning here?

 

[J_J]

Is there any restriction in your tank/return hoses.

Is your sump filters clean?

 

[emanaresi]

I don't think there is any restriction... Sump filter? I just changed the hydraulic fluid and the filter.

I don't know about any other filters. How would I know if there's a restriction?

 

[Farmerford]

It seems to me you have an intermittent total blockage in the circuit from the directional control valve work port connected to the base (closed) end of the boom cylinders. When you raise the boom fluid flows from the directional control valve to the base of the cylinders, and that fluid flows without apparent obstruction until the flow reaches a certain speed, at which point something moves to block the circuit. Since it does not happen when lowering the boom, at which time the fluid flow is reversed, the obstruction is sensitive to the direction of fluid flow.

I have had something similar happen twice. One time, the quick disconnect coupler had a weak spring on the poppet valve that closes the coupler when disconnected, and as the flow sped up through the coupler the poppet valve (actually both valves since they press against each other when the coupler is closed) moved against the weak spring and closed the connection off just as if it were disconnected.

The other time, a flap of the inner lining in a hose at the end fitting became loose and when the fluid flow increased against the open end of the flap it moved against the opposite wall of the hose and blocked the flow.

You can test for these problems by switching the connection of the boom base end and rod end quick disconnects at the valve; the valve lever will simply work the opposite direction, and if the stopping follows the hose or quick disconnect it will isolate the problem to it. You can further isolate the problem by switching the boom and bucket hoses to see when the problem moves to.

The other possibililty that comes to mind is the load check in the valve. It must open to allow fluid to flow into the base of boom cylinder on raise, and I suppose it is possible, though unlikely, that the load check opens at low flows by then closes at more rapid flows. You should also be able to test that by swapping hoses.

We are all interested in knowing what you find.

 

[J_J]

You might also remove the loader relief valve, and inspect and clean if necessary.

 

[emanaresi]

yeah, swapping hoses wil be my next troubleshooting task. Thank you.

In a similar thread I posted in the Kubota forum we were speculating there may be some small chance the spools have been switched. I don't know if that could make any sense of the problem or not.

 

[emanaresi]

JJ, I'm glad you said that. There isnt a relief valve on the control valve, it must be somewhere else on the tractor. Any thoughts on where?

 

[J_J]

Yep, look under the right side foot rest for a hyd block. Some tractor relief are located on the hyd block.

Has anyone worked on the tractor or moved any hoses?

In an open center hyd system, there is a path for the fluid to flow until it is redirected by a valve.

That is assuming that all hoses are connected and all vales are working as the should.

Now, if everything is connected correctly, and things don't work as expected, then something is broken or not operated right.

Your hyd block may look similar to this.

 

[emanaresi]

Yeah I have a hydraulic block like that. I'll check on it too. The hydraulics have been worked on. I don't know when or by who but a bradco 511 was added. It has a t fitting that attaches it into the return line and you swap it's line onto the pb port at the loader valve (there's quick connects One for 3pt hitch, one for backhoe)

 

[J_J]

With no BH installed, your hyd path should be like this.

Pump to hyd blk, then to FEL, FEL OUT back to hyd blk PB to 3pt, then to tank.

All return hoses should go to tank unimpeded.

If BH installed, then the PB out of the hyd blk would go to the IN port of the BH, and the BH OUT hose would go to a return hose.

You probably would not use the 3pt with BH connected.

The bolt on the bottom of the hyd blk, is the tractor relief.

You might check the relief pressure.

 

[emanaresi]

Yeah. That is all correct and that is how it is plumbed