John Deere 2040 with Open Center valve on FEL

[Tx Jim]

We can't solve Jimmy_G's tractors hyd problem until he reveals whether his tractors serial # is below or above 266,750

 

[LD1]

Seems alot of people don't understand a CC system.

It's alot like compressed air in your shop if you have a shop plumbed and several drops.

Anywhere in the system you can hook in a tool and have pressure. Because the air cannot escape the system....pressure builds....compressor quits pumping until you start using air.

Now have an open line....representing an open center system. It will never build pressure...compressor will run 24/7 and never build pressure.

This is why the OP's 3ph don't work. If it's closed center and his valve is open center.....it will NEVER build pressure until he deadheads a loader function like curl back and keep holding.

But until the OP ever reports back with a serial #, we just don't know

 

[Tx Jim]

LD1
I think that was a very good simplified explanation for operation of closed-center hyd system. In the past I've compared CC hyd system operation to shallow water well pump/pressure tank system. Water pump builds pressure in tank then switch cuts pump off until pressure in tank drops then switch turns pump on. Large water leak causes pump to operate continuously.

I was employed by JD dealer from '66-'87 which was a large portion of the ''main hey day of CC hyd's'' & served as a dealer service manager for the last 13 yrs helping technicians solve CC hyd system problems.

IMHO the main key to solving CC hyd problems is performing very good diagnostic procedures.

 

[LD1]

IMHO the main key to solving CC hyd problems is performing very good diagnostic procedures.

That is the main key in solving any hydraulic problem whether it's open center or closed

 

[npalen]

I like both, the shop air system and well pump system, as analogies for the closed center hydraulic system. The swash plate and pistons are at the heart of the operation.

Thinking back to the late sixties/early seventies, Cessna Hydraulics in Hutchinson KS was building a piston pump developed by Algear (Oilgear?), a German company IIRC. I didn't at the time realize why all the excitement for this "new pump" but I'm now wondering if it was a forerunner to modern day hydrostats. I believe they eventually abandoned the project as they found the cost to build excessive due to the tight tolerances required. Anyone know the history?

Edit: Perhaps the hydrostatic drive was first used by the Germans in the Panzers?

https://tanks-encyclopedia.com/ww2/****-germany/panzer-iv-mit-hydrostatischem-antrieb/

 

[Tx Jim]

I like both, the shop air system and well pump system, as analogies for the closed center hydraulic system. The swash plate and pistons are at the heart of the operation.

JD closed center hyd's on tractors built from '61-'92 do not utilize a swash plate. Those systems utilize a stroke control valve to control pumping. When stand-by pressure(2250 psi) is achieved stroke control valve opens diverting pressure oil to crankcase of main hyd pump pushing pistons away from rotating shaft which causes pumping to cease. When pressure in system drops then springs push pistons down against rotating shaft then pumping commences.

 

[Tx Jim]

That is the main key in solving any hydraulic problem whether it's open center or closed

I may be prejudice but I think good diagnostics is more important diagnosing closed center hyd's because JD CC hyd's is understood by a smaller percentage of people

 

[LD1]

I may be prejudice but I think good diagnostics is more important diagnosing closed center hyd's because JD CC hyd's is understood by a smaller percentage of people

You may be correct. But it seems hydraulics in general are understood by by a very small percentage of people.

 

[LD1]

For me....closed center is easy. Being able to simply tee everything....

You either have oil pressure or you don't. Sure there are wildcard cases like this where one uses a wrong valve.

But in open center stuff.....I thing there is a very very small percent of people that truly understand PB and how it functions.

I think everyone's natural instinct is to plumb as if it was CC (or like they would shop air). Just tap a pressure like somewhere and install valve. Hard to get people to understand and grasp the concept of PB

 

[npalen]

JD closed center hyd's on tractors built from '61-'92 do not utilize a swash plate. Those systems utilize a stroke control valve to control pumping. When stand-by pressure(2250 psi) is achieved stroke control valve opens diverting pressure oil to crankcase of main hyd pump pushing pistons away from rotating shaft which causes pumping to cease. When pressure in system drops then springs push pistons down against rotating shaft then pumping commences.

That's interesting! Any online animations showing how this works?