FEL Drops When Lever Is Pulled To Raise

[bmarshall1]

Thanks for all the replies - keep them coming as i am learning from each one. Now I know overnight drop is not a big deal and I have a direction to look into for the FEL issue. I will begin my search for a work manual or parts diagram.

 

[oldnslo]

So would a load check normally hold the load in a raised position assuming there was no cylinder piston seal leakage and require the pump to produce pressure in the rod side of the lift cylinders to lower the load?

No, a load check is in the valve to prevent oil flow from one of the work ports to the pressure port when the valve is shifted.

Example of How this works based on the following parameters:
Since the pump is being unloaded with the valve in the spring centered position pressure is minimal lets use 250 PSI
There is load on the FEL so its requires 1500 PSI to raise.

When you feather the valve to start raising you open the work port to pressure. The load check prevents the 1500 PSI oil in the work port from flowing into the 250 PSI pressure port. Once you have shifted the valve far enough to create 1500 PSI in the pressure port the oil flows from the pressure port into the work port thru the load check raising the load.

 

[LD1]

^^^^yes.

You have an open center valve.

The ports.....pressure, tank, and A and B work ports are NOT either full open or full closed.

In neutral, pressure is passing straight thru to tank.

If you pull the lever (shift the spool) fully one way....you get full flow from pressure to one of the work ports. The other port is full open to tank to return oil.from the other side of the cylinder.

The issue is when one is trying to slowly feather the valve. The spool isn't fully shifting. You are just cracking the the work port open to the pressure, to limit it's flow and speed. But the balance of pump oil is still returning via low pressure to tank.

So there is technically two flow paths for pump oil to take. Some returns to tank, some goes to loader cylinder.

The load check is what keeps the pressurized cylinder oil (pressurized from gravity), from overpowering pump oil and just returning to tank and dropping your loader.....when all you are trying to do is raise it slowly...

Which is why they are sometimes refered to as anti-drop valves.

 

[npalen]

So if the engine is not running will the loader drop if you shift the valve to the "lower" position or does the check valve hold the load up? Seems like something would need to open the check valve with no pump pressure input.
Sorry for all the questions but hope they will help the OP understand also.

 

[oldnslo]

So if the engine is not running will the loader drop if you shift the valve to the "lower" position or does the check valve hold the load up? Seems like something would need to open the check valve with no pump pressure input.
Sorry for all the questions but hope they will help the OP understand also.

With the engine off and you shift the valve to lower position the loader will drop. On the attached document the red check valve is the load check valve. The valves are drawn in the shifted position showing how a series parallel valve works but the load check would be the same for a standard parallel valve also.

 

[npalen]

Can you clarify the terms "piston broken" and "piston was missing"? I think I see how the check valve is bypassed to drop the load with no pump pressure but those two terms are a bit confusing.
Thanks for posting.

 

[oldnslo]

Can you clarify the terms "piston broken" and "piston was missing"? I think I see how the check valve is bypassed to drop the load with no pump pressure but those two terms are a bit confusing.
Thanks for posting.

Guess I should have looked at the schematic a little closer. I created this schematic as an attempt to explain a failure on a different posting. The failure was why would the FEL raise only when the curl or dump was bottomed out. He found that one of his lift cylinder pistons was broken.

Sorry for the confusion.

 

[npalen]

Any luck figuring out your issue, Bruce? (bmarshall1)

EDIT: Pic shows items 1-6 as components of the load check on what I believe is a Prince valve. I'm wondering if this might be somewhat similar to your loader valve.

 

[bmarshall1]

Hi npalen,

I have to put it on the back burner for a bit, we are currently remodeling our home and the tractor works sufficiently but at a certain point I wold like it to work as intended. Thank you for the diagram (and everyone for their ideas and questions).

npalen - is what you attached specifically for the ex3200? for some reason when I open it it turns sideways and cuts off the bottom, can you send me a link or try to reattach.

Lastly, the seller gave me a weight rack (and 5 suitcase weights), it is a rectangular bracket about 16 x 6 inches but I see no place to mount it, any thoughts?

 

[npalen]

I left off the bottom of the illustration as it was irrelevant. The valve shown is generic and wouldn't necessarily apply to your setup. I just thought it might help locate the load check on your valve so you could see if it needs repair. Be sure to set the loader on the ground so the pressure is off before messing with the valve!

P.S. Send some of that warm Florida sunshine to Kansas please!