# John Deere 750 Hydraulic problem.



## Richard O. Braun (Apr 14, 2019)

Hopefully somebody can help me with this issue. Have an 87 J.D.750 with a 67 loader. Having a problem with the bucket cylinders collapsing, I'll try to explain. With the boom raised and the bucket tilted downward ( rods extended), as I lower the boom and the edge of the bucket touch's the ground and I continue to lower, the rods collapse back into the cylinders. As I raise the boom, the rods extend out of the cylinders, to their original position. The bucket action on kurlling direction is fine and strong, the bucket action on dumping is rather slow. The rest of the hyd. system seems to work fine. I have had the bucket cylinders checked at a local shop and they tell me that the cylinders are fine and that the packing looks good. I have also installed a shut off valve at the barrel end of the cylinders. With the valves closed, thus blocking the fluid within the cylinders, the bucket still collapses. Also, with valves closed, when the bucket lever is pushed forward (dumping), the rods will still extend. Any information would be appreciated.


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## Hoodoo Valley (Nov 14, 2006)

Welcome to the forum Richard! Does your loader have a "float" position? Do you have a "re gen" position lock out? If so, I'd try putting it in the re gen position so that the bucket is hydraulically dumping rather than released and gravity dumping. It might make a difference.


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## Richard O. Braun (Apr 14, 2019)

Hoodoo Valley said:


> Welcome to the forum Richard! Does your loader have a "float" position? Do you have a "re gen" position lock out? If so, I'd try putting it in the re gen position so that the bucket is hydraulically dumping rather than released and gravity dumping. It might make a difference.


Yes it has a "float" position. Not sure what a re gen. position lock out is, haven't seen any mention of that in the manuals. The float position is on the boom control. Something I forgot to mention, I've heard about cylinder "bypass", but can a cylinder have "bypass" in only one direction? Thanks, Rich


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## Hoodoo Valley (Nov 14, 2006)

Yes. Regen is a "feature" of most modern FEL (Front End Loader) valves, it's on the Dump (joystick far right) circuit, and is also referred to as "Fast Dump". The reason it is nice to have is that without it, the weight of a filled bucket can actually "pull" the bucket down faster then the fluid can enter the other side of the cylinder, this will create a air pocket and give the bucket a "floppy" feeling until the joystick is held in the dump mode a few seconds to refill the cylinder pushing the air past the seals. So we add "regen" or "regenerative" function to the valve. 

Regen solves this problem by actually filling both sides of the cylinder at the same time with hydraulic fluid. But how will that work you might ask? Well, because there is more volume on the side of the cylinder that extends it since the rod is taking up space in the other side, it "overpowers" the rod side and lets the cylinder extend-thereby dumping the bucket. So since now both sides of the cylinder are "pressurized", the air pocket can not develop, eliminating the "floppy" bucket syndrome. One other added bonus is that the bucket actually dumps faster due to the higher flow rate required to do all this, that's why it's referred to as "fast dump" sometimes.

So, now you may be asking “This is cool and all that, but why do I need to know about it?” The answer to that is simple, if you ever try to run a snow plow with two SA (single acting) cylinders, or a cylinder that drives a chute rotator on a snowblower you will soon find out that they won’t work if you push the joystick to far right in the regen mode. The plow won’t work because since both lines are pressurized-both cylinders will be trying to extend at the same time binding everything up. The rotator won’t work because there is no weight pushing the cylinder closed like there is on the loader. 
On most, if not all John Deere tractors there is a “lockout” the limits how far the joystick travels to the right to keep it out of the regen mode.


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## Richard O. Braun (Apr 14, 2019)

PROBLEM SOLVED!! Well after going thru all of that, I discovered that my problem was that the quick connect on my control valve was not opening due to a bad male end of the quick connect. Fluid was coming from the control valve but could not get past the quick connect. Never thought of a problem there because all of the quick connects were new.


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