6420 no hydraulic power to (3)rear 300 series SCV'S

[wore out]

Hmm, 500 psi with nothing actuated, that's interesting. Sounds like something is leaking by and dumping into the load sense circuit. I'll do some more digging and maybe wore out or WTW will have some better ideas.

Got your message, I'll try when I get home tonight

IIRC, that is normal standby pressure?

 

[620 John]

IIRC, that is normal standby pressure?

I'll look again but what I'm seeing in the tech manual is the load sense is supposed to 30-80 psi with nothing actuated. I think there's supposed to be a differential pressure of 400+ psi of system pressure vs load sense pressure. I'm a little rusty on this stuff, I'll double check when I get home

 

[wore out]

I'll look again but what I'm seeing in the tech manual is the load sense is supposed to 30-80 psi with nothing actuated. I think there's supposed to be a differential pressure of 400+ psi of system pressure vs load sense pressure. I'm a little rusty on this stuff, I'll double check when I get home

So he is checking at the "load sense port"

 

[KCinNMO]

I’d like to give it a shot about what I –think- I understand about the SCV’S operation.

All the ‘flat’ shuttle valves are pushed ‘open’ by the LS pressure. When a SCV is operated ‘higher pressure’ pushes it’s valve ‘closed’ and directs higher pressure onto the LS line. This higher pressure is a ‘signal’ to the pump to supply more hydraulic pressure -to the SCV area-.

If that is correct and if what I am reading at the connection is LS pressure. Which as I understand should be below 100 psi, it would appear that –‘perhaps’ a shuttle (flat) valve is stuck, not necessarily in the SCV area . . . . or- something else is leaking pressure into the LS circuit.
But. . . . if the valve was stuck, why isn't the high pressure being supplied.

 

[wore out]

I’d like to give it a shot about what I –think- I understand about the SCV’S operation.

All the ‘flat’ shuttle valves are pushed ‘open’ by the LS pressure. When a SCV is operated ‘higher pressure’ pushes it’s valve ‘closed’ and directs higher pressure onto the LS line. This higher pressure is a ‘signal’ to the pump to supply more hydraulic pressure -to the SCV area-.

If that is correct and if what I am reading at the connection is LS pressure. Which as I understand should be below 100 psi, it would appear that –‘perhaps’ a shuttle (flat) valve is stuck, not necessarily in the SCV area . . . . or- something else is leaking pressure into the LS circuit.
But. . . . if the valve was stuck, why isn't the high pressure being supplied.

''This higher pressure is a ‘signal’ to the pump to supply more hydraulic pressure -to the SCV area''

Not only to the SCV area.

When the pump controller on the pump is signaled to increase PUMP flow/pressure, which shows up at the SCV's, the 3-point valve, the "power beyond" loader valve, etc.

''something else is leaking pressure INTO the LS circuit"

You have the OPPOSITE problem, signal pressure from the SCV's is NOT getting into the LS circuit or leaking OUT.

''if the valve was stuck, why isn't the high pressure being supplied''

I'm NOT sure which exact valve you may be referring to?


Going back several of my posts to the "inlet priority valve" it's purpose is to be sure the STEERING circuit gets flow before releasing any to other functions.

 

[KCinNMO]

''This higher pressure is a ‘signal’ to the pump to supply more hydraulic pressure -to the SCV area''

Not only to the SCV area.

When the pump controller on the pump is signaled to increase PUMP flow/pressure, which shows up at the SCV's, the 3-point valve, the "power beyond" loader valve, etc.

''something else is leaking pressure INTO the LS circuit"

You have the OPPOSITE problem, signal pressure from the SCV's is NOT getting into the LS circuit or leaking OUT.

''if the valve was stuck, why isn't the high pressure being supplied''

I'm NOT sure which exact valve you may be referring to?


Going back several of my posts to the "inlet priority valve" it's purpose is to be sure the STEERING circuit gets flow before releasing any to other functions.

Don't mean to be confusing, just trying to better understand the operation.
I thought if the pressure at the LS connection at -connection A- was high it would have meant something was 'requesting' pressure.

If -something- requests more pressure is there a diverter valve someplace that would direct the pressure to the 'requester' ?

How is the LS 'signal' routed so the high pressure knows who's requesting it ?

"When the pump controller on the pump is signaled to increase PUMP flow/pressure, which shows up at the SCV's, the 3-point valve, the "power beyond" loader valve, etc."
Then if I operated the 3-pint hitch and also moved the levers on an SCV should it have high pressure/flow ?

Just trying to come up with ways to help isolate whats going on.

 

[wore out]

Don't mean to be confusing, just trying to better understand the operation.
I thought if the pressure at the LS connection at -connection A- was high it would have meant something was 'requesting' pressure.

If -something- requests more pressure is there a diverter valve someplace that would direct the pressure to the 'requester' ?

How is the LS 'signal' routed so the high pressure knows who's requesting it ?

"When the pump controller on the pump is signaled to increase PUMP flow/pressure, which shows up at the SCV's, the 3-point valve, the "power beyond" loader valve, etc."
Then if I operated the 3-pint hitch and also moved the levers on an SCV should it have high pressure/flow ?

Just trying to come up with ways to help isolate whats going on.

I don't think 100 psi in the control circuit is REAL significant, at least at this point and is NOT the cause of your "no flow" problem, I don't think.

The brake valve HAS been known to develop internal problems that can direct oil into the control circuit, but that keeps pump at high pressure all the time (NOT good), but wouldn't cause a "no flow to the SCV's" issue.

When the pump goes to a high pressure, the SCV's, loader valve and hitch valve ALL are in parallel, nothing "directs" that pressure and resulting available flow to one or another.

In the case of the pump not being able to make much flow the "priority valve" directs what flow there is to steering, and (IIRC) regulates steering and brake maximum pressure.

I don't know enough about the "innards" of the SCV's to know what could have possibly happened after you worked on them.

The "dime valves" control the direction of the control circuit oil flow so that the SCV needing the most pressure controls the pump pressure, even if something is wrong with how/where they are installed that wouldn't affect the pump FLOW to the SCV's when the loader valve is being activated and the pump pressure is up as they SCV's are fed in PARALLEL with the loader valve.

(The couplers on the SCV's don't have pressure/flow even when the loader valve is being activated, correct?)

OK! So the "light" just went on here!

You have three electronically-operated valves and NONE work, even the two you didn't have apart, while other functions DO work.

I'll bet something has happened on the electronic/electrical side, is there a common (to all the valves) harness connector that could be dislodged, or a chafed wire that could have caused a fuse to blow?

 

[KCinNMO]

I don't think 100 psi in the control circuit is REAL significant, at least at this point and is NOT the cause of your "no flow" problem, I don't think.

The brake valve HAS been known to develop internal problems that can direct oil into the control circuit, but that keeps pump at high pressure all the time (NOT good), but wouldn't cause a "no flow to the SCV's" issue.

When the pump goes to a high pressure, the SCV's, loader valve and hitch valve ALL are in parallel, nothing "directs" that pressure and resulting available flow to one or another.

In the case of the pump not being able to make much flow the "priority valve" directs what flow there is to steering, and (IIRC) regulates steering and brake maximum pressure.

I don't know enough about the "innards" of the SCV's to know what could have possibly happened after you worked on them.

The "dime valves" control the direction of the control circuit oil flow so that the SCV needing the most pressure controls the pump pressure, even if something is wrong with how/where they are installed that wouldn't affect the pump FLOW to the SCV's when the loader valve is being activated and the pump pressure is up as they SCV's are fed in PARALLEL with the loader valve.

(The couplers on the SCV's don't have pressure/flow even when the loader valve is being activated, correct?)

OK! So the "light" just went on here!

You have three electronically-operated valves and NONE work, even the two you didn't have apart, while other functions DO work.

I'll bet something has happened on the electronic/electrical side, is there a common (to all the valves) harness connector that could be dislodged, or a chafed wire that could have caused a fuse to blow?

"You have three electronically-operated valves and NONE work, even the two you didn't have apart, while other functions DO work."

Sorry if I didn't make it clear earlier. The SCV are ALL -mechanically controlled- - NO electrical connections involved, ALL mechanical.

I tried moving the bucket and operating an SCV, NO flow from a hose connected to the SCV.

Operation wise the SCV shuts off -all- hydraulic flow -unless- it is -pulled or pushed (mechanically) from neutral. Then it -directs the flow either to upper or lower outlets.

It makes no sense (to me) that there is no flow in any SCV while the 3- point /rock shaft works.
It appears (to me) that the SCV and the rock shaft are on the same 'feed line'.

 

[Fixingfarmer]

I'll try the PM thing if I don't get a response, but I just posted the reply a couple hours ago.
I think getting a Deere dealer to print off a repair manual page would be impossible. There is no way they would want to lose out on a repair job by helping someone fix a problem.
I'll just have to keep on digging for more information and maybe I'll be able to find out enough about how the hydraulics flow that I can figure it out.
As I did not even touch SCV #3 it makes no sense to me why it wouldn't work.

You might be surprised. Don’t go to a lawn and garden type or medium sized snow pusher estate tractor place try one of the dealers where the big boys go. If they are busy with 8 and 9Rs they might hand you that info pretty quick...is there a hydraulic lockout switch on it? You found a broken pin though...

 

[KCinNMO]

You might be surprised. Don’t go to a lawn and garden type or medium sized snow pusher estate tractor place try one of the dealers where the big boys go. If they are busy with 8 and 9Rs they might hand you that info pretty quick...is there a hydraulic lockout switch on it? You found a broken pin though...

Thanks. There's not too many 'lawn and garden' places around here in farming country.
Getting help in an AGRA dealer would cost thousands of $. They don't give it for free. Nowadays -no one- actually knows how things work. They just follow -flow charts- and -replace parts-. Until you go broke or they give up.

The knowledge to repair a tractor is in the old folk, long since retired, but willing to help.

 

[Fixingfarmer]

Thanks. There's not too many 'lawn and garden' places around here in farming country.
Getting help in an AGRA dealer would cost thousands of $. They don't give it for free. Nowadays -no one- actually knows how things work. They just follow -flow charts- and -replace parts-. Until you go broke or they give up.

The knowledge to repair a tractor is in the old folk, long since retired, but willing to help.

I can think of 3 dealers around that are willing to just hand me the book and specialty tools. Sometimes it’s about the attitude and asking the right question. One of them is a branch of the largest dealer in the state. They know if they don’t help me I’ll get help at one of the others. Or worse to them find a different color tractor to buy next and tell the neighbors. The service department is an incredible expense. When I worked at caterpillar we had company cell phones. 2500 techs with a cell phone and a Verizon card for the computer. Their cell phone bill was 49500 a month. Sales is where the money is and promotion of their paint color. They don’t get that by not being helpful and there are still a few out there who understand that.

 

[Fixingfarmer]

I can think of 3 dealers around that are willing to just hand me the book and specialty tools. Sometimes it’s about the attitude and asking the right question. One of them is a branch of the largest dealer in the state. They know if they don’t help me I’ll get help at one of the others. Or worse to them find a different color tractor to buy next and tell the neighbors. The service department is an incredible expense. When I worked at caterpillar we had company cell phones. 2500 techs with a cell phone and a Verizon card for the computer. Their cell phone bill was 49500 a month. Sales is where the money is and promotion of their paint color. They don’t get that by not being helpful and there are still a few out there who understand that.

If you go in there and say gimme the books I wanna fix this myself so you don’t charge me my life savings they won’t help you ask their opinion on what’s going on and tell them what you have done already. They will probably walk out to the shop grab the right guy and you might get some where

 

[KCinNMO]

If you go in there and say gimme the books I wanna fix this myself so you don’t charge me my life savings they won’t help you ask their opinion on what’s going on and tell them what you have done already. They will probably walk out to the shop grab the right guy and you might get some where

You are very fortunate. That sounds like the way it used to be around here until Deere started closing the smaller older dealerships and -consolidating-. I knew a Deere sales guy that would do exactly that until he retired. He'd walk you out to the shop floor, find the guy that knew something and tell him the problem. There also used to be a dealer near where they would do anything to help.

Last year I went to 2 Deere dealers looking to buy a new 5M series tractor about the size of a 6420 or a little larger. Not only did they seem disinterested but the somewhat young sales staff knew less about the tractors than I did. I finally just gave up. So I have to repair what I've got.

 

[Fixingfarmer]

You are very fortunate. That sounds like the way it used to be around here until Deere started closing the smaller older dealerships and -consolidating-. I knew a Deere sales guy that would do exactly that until he retired. He'd walk you out to the shop floor, find the guy that knew something and tell him the problem. There also used to be a dealer near where they would do anything to help.

Last year I went to 2 Deere dealers looking to buy a new 5M series tractor about the size of a 6420 or a little larger. Not only did they seem disinterested but the somewhat young sales staff knew less about the tractors than I did. I finally just gave up. So I have to repair what I've got.

That’s a shame that that has occurred in your local. Like I said before if you walk into the powersports side here or the dealers closer to a metro area here you get that but the ag guys still get it, if they didn’t who would buy that 200000 dollar or more tractor? If you do get to the ultimate frustration point I know some people who would help by your name chilicothe can’t be too far away if you are willing to try the other green flavor...they have a phone line and dedicated techs staffing it that can step you through almost anything. I won’t give the name as the manufacturer tracks feedback online like nobody else I got an attaboy once that got pizza for the shop because 4000 views happened on something and I don’t like that big brother aspect but you can figure it out and the service will be there like you wouldn’t believe. Good luck finding your problem!

 

[KCinNMO]

That’s a shame that that has occurred in your local. Like I said before if you walk into the powersports side here or the dealers closer to a metro area here you get that but the ag guys still get it, if they didn’t who would buy that 200000 dollar or more tractor? If you do get to the ultimate frustration point I know some people who would help by your name chilicothe can’t be too far away if you are willing to try the other green flavor...they have a phone line and dedicated techs staffing it that can step you through almost anything. I won’t give the name as the manufacturer tracks feedback online like nobody else I got an attaboy once that got pizza for the shop because 4000 views happened on something and I don’t like that big brother aspect but you can figure it out and the service will be there like you wouldn’t believe. Good luck finding your problem!

BTW -I messaged you so this problem thread doesn't get muddled up.

 

[KCinNMO]

I don't think 100 psi in the control circuit is REAL significant, at least at this point and is NOT the cause of your "no flow" problem, I don't think.

The brake valve HAS been known to develop internal problems that can direct oil into the control circuit, but that keeps pump at high pressure all the time (NOT good), but wouldn't cause a "no flow to the SCV's" issue.

When the pump goes to a high pressure, the SCV's, loader valve and hitch valve ALL are in parallel, nothing "directs" that pressure and resulting available flow to one or another.

In the case of the pump not being able to make much flow the "priority valve" directs what flow there is to steering, and (IIRC) regulates steering and brake maximum pressure.

I don't know enough about the "innards" of the SCV's to know what could have possibly happened after you worked on them.

The "dime valves" control the direction of the control circuit oil flow so that the SCV needing the most pressure controls the pump pressure, even if something is wrong with how/where they are installed that wouldn't affect the pump FLOW to the SCV's when the loader valve is being activated and the pump pressure is up as they SCV's are fed in PARALLEL with the loader valve.

(The couplers on the SCV's don't have pressure/flow even when the loader valve is being activated, correct?)

OK! So the "light" just went on here!

You have three electronically-operated valves and NONE work, even the two you didn't have apart, while other functions DO work.

I'll bet something has happened on the electronic/electrical side, is there a common (to all the valves) harness connector that could be dislodged, or a chafed wire that could have caused a fuse to blow?

Update:
After looking at the schematics till I went blind I couldn’t see how the rock shaft would work but the SCV’S didn’t.

I connected the gauge to the system 500 psi power port. The 3 point moves up and down just fine but with little pressure increase. Pressure stays around 500 psi with a slight increase. I didn’t realize this before as I don’t have anything hooked up and it appeared to work OK.

Yet still NO hydraulic oil output from hose connected any SCV.

So what’s going on? No LS feedback?

 

[wore out]

Update:
After looking at the schematics till I went blind I couldn’t see how the rock shaft would work but the SCV’S didn’t.

I connected the gauge to the system 500 psi power port. The 3 point moves up and down just fine but with little pressure increase. Pressure stays around 500 psi with a slight increase. I didn’t realize this before as I don’t have anything hooked up and it appeared to work OK.

Yet still NO hydraulic oil output from hose connected any SCV.

So what’s going on? No LS feedback?

Which of the 3 SCV's did you have apart, left, center, or right?

At this point I'd be tempted to remove that SCV, and be SURE the remaining"dime valves" between the sections are in place and put the left end cap on with washers on the studs to make up for the thickness of the removed SCV and start it up and see what happens.

 

[KCinNMO]

Which of the 3 SCV's did you have apart, left, center, or right?

At this point I'd be tempted to remove that SCV, and be SURE the remaining"dime valves" between the sections are in place and put the left end cap on with washers on the studs to make up for the thickness of the removed SCV and start it up and see what happens.

It was #2. Just to make sure the flat valves were in I already disassembled them ONCE after I put things back together the -first time-. At that time the shuttle valves were all there. I also verified the seals were in place.
However as this was the only thing done I am probably going to disassemble things again.

As a last resort I have even been considering getting short bolts and putting the left end plate on without SCV #1 & #2.
The way the SCV'S are mounted makes it just as difficult to remove one. New bolts must be installed because of the LONG double end threaded screw bolts (shafts) used, which won't work. Just removing the SCV'S requires disassembling the rock shaft to get SCV'S off the long bolts that screw into the center control block.

I understand that -the last thing done should be checked -AGAIN- as it's the likely problem. . . . .What did you do last? Undo it!

I have been trying to blame myself and what I did or something I missed. So far it all doesn't make sense to me.

I'd think if a flat (shuttle) valve is missing the particular SCV which controlled it would not -trigger- the LS and not get high hydraulic pressure to pump up but everything else would as the LS should still be -passed along-. That is what the left end plate does, unless there is a shuttle valve (NOT required in mine) there it passes the LS pressure.
But even if the high pressure is there to -everything- why is there no flow from a SCV connection?
. . . . . I guess what really need to try and K.I.S.S. it.

 

[wore out]

It was #2. Just to make sure the flat valves were in I already disassembled them ONCE after I put things back together the -first time-. At that time the shuttle valves were all there. I also verified the seals were in place.
However as this was the only thing done I am probably going to disassemble things again.

As a last resort I have even been considering getting short bolts and putting the left end plate on without SCV #1 & #2.
The way the SCV'S are mounted makes it just as difficult to remove one. New bolts must be installed because of the LONG double end threaded screw bolts (shafts) used, which won't work. Just removing the SCV'S requires disassembling the rock shaft to get SCV'S off the long bolts that screw into the center control block.

I understand that -the last thing done should be checked -AGAIN- as it's the likely problem. . . . .What did you do last? Undo it!

I have been trying to blame myself and what I did or something I missed. So far it all doesn't make sense to me.

I'd think if a flat (shuttle) valve is missing the particular SCV which controlled it would not -trigger- the LS and not get high hydraulic pressure to pump up but everything else would as the LS should still be -passed along-. That is what the left end plate does, unless there is a shuttle valve (NOT required in mine) there it passes the LS pressure.
But even if the high pressure is there to -everything- why is there no flow from a SCV connection?
. . . . . I guess what really need to try and K.I.S.S. it.

The "dime valve"/check valve for the specific function OPENS when that function is activated, allowing oil to flow into the LS circuit and ALL other function dime valves/check valves are forced closed against their seats so LS oil pressure can't back flow to those functions and leak away.

If more than one function is operated at the same time the one requiring the highest pressure would force it's check valve open and the others closed, so the one requiring the highest pressure "rules"

So if you are missing a check valve for a certain function, that specific function wouldn't be affected when being used.

OTHER functions WOULD be affected, though, because of LS oil being able to backflow into the valve for the function NOT being activated and "to sump", rather than building pressure in the line to the pump controller.

It's been a LONG time since I've worked with these "valve stacks", I wonder if there's a "spot" where a "dime valve" would fit, but isn't supposed to have one that would block the LS flow if a "dime valve" is installed there in error?

As to taking the "blocks" off, IIRC, one can unscrew the studs and remove them rather than disassembling other parts to allow for the removal of the "blocks"/SCV's.

 

[KCinNMO]

The "dime valve"/check valve for the specific function OPENS when that function is activated, allowing oil to flow into the LS circuit and ALL other function dime valves/check valves are forced closed against their seats so LS oil pressure can't back flow to those functions and leak away.

If more than one function is operated at the same time the one requiring the highest pressure would force it's check valve open and the others closed, so the one requiring the highest pressure "rules"

So if you are missing a check valve for a certain function, that specific function wouldn't be affected when being used.

OTHER functions WOULD be affected, though, because of LS oil being able to backflow into the valve for the function NOT being activated and "to sump", rather than building pressure in the line to the pump controller.

It's been a LONG time since I've worked with these "valve stacks", I wonder if there's a "spot" where a "dime valve" would fit, but isn't supposed to have one that would block the LS flow if a "dime valve" is installed there in error?

As to taking the "blocks" off, IIRC, one can unscrew the studs and remove them rather than disassembling other parts to allow for the removal of the "blocks"/SCV's.

Thanks for the backflow explanation. I wouldn't have expected the LS would go back thru a function that wasn't activated.
Yep, I understand the stud business. The problem is the bottom stud is so long that it hits the 3 point arm when pulling it out. The other two are easy.
I took things apart again. The flat valve next to SCV #2 was gone. When I disassemble and assemble things I always have a large cloth covering the whole area and when done I run a strong roll around magnet 'nut, screw picker upper' around in case I missed anything. I also put vasoline on it to hold it in place when installing. So I don't know where it could have gone.

When I wiped the area where the valve was supposed to be the oil had a 'blackish' color to it like it had some metal particles in it. You don't suppose the valve came apart?

Anyway I put a new flat shuttle valve that I had in and put things back together.
End result- no change-. Next thing is I'll do is pick up 3 short bolts to replace the studs remove #1 & #2 SCV and put only the end plate in.

I can't really check the LS pressure because I have a 300 series SCV in position #3 which requires a 'tap' to be inserted in the line off the R end plate. I don't have the JD parts to do that.