310a slow hydraulics help

[ala.millwright]

Okay guys I need some help. not sure what year but late model 310a deere. The hydraulics are very slow and it won't do two functions at same time whether its backhoe or loader. The main pummp is new,filters new and checked suction screen in trans. I do know I have a control valve bypassing on backhoe main boom and possibly loader bucket. What I'm wonder is there anyway to check charge pummp without splitting tractor in half? On the main pump I've checked pressure at the two ports on right side and pressure is good on both ports. Please HELP.

 

[ala.millwright]

Does anyone have any ideas to check other than charge pump

 

[bentwrench22]

If preasure is at factory specs at control valve or at pump you have already checked charge pump most jd use varible piston pumps and won't pump with out charge pump ,,maybe pull spools from control valve to see if spool is broken if you belive oil is crossing in system

 

[willie59]

Here's a link to the spec sheet.
http://www.deere.com/en_US/cfd/cons...non_current_pdfs/noncurrent_backhoes/310A.pdf

It says the machine has closed center hydraulics and a high stanby pressure. Maybe an internal load sensing piston pump? :beatsme

What makes you think you have control valves bypassing? Care to elaborate on that?

 

[ala.millwright]

Thanks! I've been told that if charge pressure is good then nothing wrong with charge pump. Could charge pump not have enough flow but still have correct pressure?? I disconnected the feed lines to backhoe and plugged them but had no effect on loader operation. If a loader control valve is bypassing will this slow down loader and not let it do two things at one time? The longer I run it the worse it gets.the loader is worse than backhoe but I know for sure main backhoe boom valve is bypassing.

 

[ala.millwright]

At one time I had the tech manual for these machines. In the control valve section it says the control valves do not let oil pass through unless valve has been actuated so what I did was disconect the lines from valve to cylinder and cranked it up, oil shot out of valve passed backhoe boom

 

[willie59]

I don't know the 310A hyd circuit, can't help ya much with specifics of the machine, and the Deere site only has spec sheets, no schematics. I can only say to have a 2,300 psi standby pressure on a closed center circuit; you can only do this one of two ways. 1) fixed displacement pump (like a gear pump) with a differential sensing valve (a flow control valve of sorts) or, 2) variable displacement pump (piston, axial, hydrostat, a few names) with either internal load sensing or external load sensing circuits. The first thing you would do is check to see if you have the spec standby pressure. You mentioned the longer you run it the worse it gets. Is that with every use it gets worse? Or; as you use it, it gets worse, shut it down, next day it's working, then as you use it, it gets worse? BTW, I just read your last post, gotta noodle that in my head.

 

[ala.millwright]

It has variable displacement piston pump. What I meant is the longer I run it the worse it gets then shut it down let it cool off and its as good as its gonna get. Even when its cool it wont do two things. What do you think about charge pump not providing enough flow but has correct pressure? I forgot this the charge pump is a fixed displacement gear pump in trans there is a pressure control valve mounted on side of trans. I don't remember just what it does.

 

[willie59]

Man you got a crazy problem. And it don't help that I don't know the hyd circuit of the machine! And...I've never seen a combination of problems that you are describing.

The charge pump; If you got on the machine, raised the loader arms, lower them, raise them, lower them, maybe even drop the bucket on the ground and raise the machine by lowering the arms. If it will do this, I doubt you have a charge pump problem.

And, if I understand you correctly; as you run it...it gets worse, then, after cool off, we're back where we started to do the same thing over again. That sounds like a problem related to heat, whether from a worn pump or malfunction of a valve, not certain which yet. And this doesn't even address the problem of not being able to run two functions at once, I haven't figured how these two problems connect yet. BTW, does the hyd circuit work the steering? Or is it a seperate system with its own pump? If hyd systems steers it, how well does steering work? Just curious.

I think I'd check the standby pressure, whatever it is, and note it at startup. And check the case drain at the pump at start up. Connect a hose to the case drain fitting on the pump, place hose in an empty bucket, and start engine. Note how much oil goes into bucket in a minute. Then, run the machine until it craps out. What's the standby pressure now? Connect to the case drain, how much goes into the bucket now?

 

[ala.millwright]

Hey tell me about it! I've been pulling my hair out dpe awhile now. I don't remember how its all connected but it does have hyd steering. Attached to bottom of steering column is a pump or either some type of directional valve that sends oil one way or the other. I've had some older guys that worked for deere when these were new tell me that when i change the reverser from foward to reverse if it changes directions without hesitation that its not charge pump. Mine does this fine. Then I've got guys tell me can't be nothing but charge pump. This is really gotten me. I'm a industrial millwright and deal with hydraulics but not like this. Oh I keep forgetting stuff! If while steering I work the backhoe the steering gets tight for just a second. Working the loader has no effect on steering.

 

[willie59]

Wow would I like to see a schematic right about now!

That thing at the bottom of the steering column is called an orbital valve.

As for the loader and hoe having different effects on steering, I'm getting overwhelmed with info. These are all clues to what the ultimate problem is, and one's I would ordinarily take note of, but the lack of knowledge of this system is a detriment for me in this case. Let's keep it simple for the moment, unless a Deere tech jumps in here to help us out. Let's check the pump like I said earlier and see what info that gives us. And, if "old Deere techs" told you this about the charge pump...I believe I would yield to their experience for now.

 

[ala.millwright]

Okay I will do it monday as I am away this weekend

 

[willie59]

To clarify what the spec sheet says about your machine, it's a "closed center" hyd circuit. That means, when no control valves are being operated, everthing in neutral, the control valves are a hyd dead end. The control valves, in neutral, do not allow oil to flow to cylinders, and there is no return to tank as well. It's a flat out dead end for the oil. That's where the pump develops the 2,300 lbs standby pressure. The hydrostat pump delivers oil. But since it's delivering to a dead end, oil ain't flowing. Pressure builds, until it reaches 2,300 lbs. Once that's achieved, the pump moves the swash plate and "destrokes" the pump and quits trying to deliver oil (flow). It holds the swash plate at a position that simply maintains this 2,300 psi of pressure against a dead end with no oil flowing. Then, you select a function (raise arms), that activation of a function causes the 2,300 lbs of pressure to drop, because now oil is flowing (to the raise arms function). The "sensor circuit" of the pump notices this pressure drop and moves the swash plate to produce more oil flow to compensate for demand. That's pretty much how your system works. It doesn't begin to understand your problem. But you have to know how it works before you can understand what the problem is, and we haven't even got into the "power beyond" of the valves that allows you to work more than one function at one time. We'll get into that later.

 

[bentwrench22]

did you put a presure gauge on the lift arms or the hoe to see what working presure is at the cylinders in question if bouth are low presure not to specs yes you have a problem .I belive you need a flow gauge to check flow volume from pump ,you might talk to dealer on some j d pumps there is an ajustment externaly for presure ,,,,But with out proper gauges you can hurt pump or weakest link with to much presure, If done wrong

 

[ala.millwright]

I haven't tried gauges on cyl or control valve. A flow meter would be great but these are pricey.I've been told how to do flow check shade tree style by taking filter off and placing a bucket under tractor with some gallon marks on bucket. They told me crank tractor and let charge pump oil flow into bucket for like 10 seconds see how much oil is in bucket and multiply by 6 and that will give me charge pump flow for 1 minute. However not to sure about this. What do you guys think?

 

[bentwrench22]

I wouldn't do that youre looking at a $ 2 to 3000.00 doller pump and you have a expensive core charge if you run pump dry it moves alot of oil if you have to change it .you want a good core ,,,you could check case drain like atco said but with out real numbers or p.s.i. you can spend a lot of money and still fix any thing ..what i would do go to parts store and buy at least a 3000 psi oil filled gauge put it on the line to lift cylinder on boom run till starts to loose power check gauge do same for hoe cylinder ,,,,if preasure is 500 psi under spec sheet you have a pump bad or needs ajust ment ,,if you talk to a knowageabul shop guy he could tell if ajustments can be made or a rebuilt pump will fix

 

[ala.millwright]

I will try that also. My main pump is new or it has less than 50 hrs on it now. Any idea how much acceptable case drain flow should be?

 

[willie59]

I've been told how to do flow check shade tree style by taking filter off and placing a bucket under tractor with some gallon marks on bucket.

Don't think that will work on this machine. Remember, the spec sheet says you have a closed center circuit and 2,300 psi standby pressure. This means when it's running and no functions are being used, all valves in neutral, there is no oil flowing out of pump, and no oil is returning to tank via tank filter line. The oil in the pump output line is static, at 2,300 psi, until you work a function, then the oil flows from pump, and the pump increases output according to the demand of the function being operated.

I will try that also. My main pump is new or it has less than 50 hrs on it now. Any idea how much acceptable case drain flow should be?

Whoa! Are you saying your main hyd pump for the machine has less than 50 hrs on it??? At what point did you begin to have these problems?

 

[ala.millwright]

Yes the main pump is new. The machine was doing this when I bought it so I replaced pump.this is why in my mind I've kinda ruled out main pump and focused on charge pump now and control valves. When I said I took lines off vontrol valve for main backhoe boom and oil shot passed boom am I correct in thinking the valve is bypassing

 

[willie59]

Yes the main pump is new. The machine was doing this when I bought it so I replaced pump.this is why in my mind I've kinda ruled out main pump and focused on charge pump now and control valves. When I said I took lines off vontrol valve for main backhoe boom and oil shot passed boom am I correct in thinking the valve is bypassing

My bad...I went back and looked at your original post, you did say you replaced the main pump. Man...too much junk in my head! :Banghead I'm still trying to figure out how oil shoots out that far when you took the boom hoses loose. The A and B ports of a valve are blocked from the supply when in neutral, whether the valve is open or closed center. Yes, it's normal to have a small amount of leakage (bypassing as you refer to it) between valve spools and bore of valve body. Obviously, if the spool was so tight inside a bore that no leakage would happen, it would be so tight you wouldn't be able to move the spool. What you would normally see if you took the two hoses off of the valve body that controls the boom with the engine running is a small amount of oil flowing out the hose ports. If the spool was broken, you wouldn't be able to boom up and down. One function, either up or down, would not work. Man would I love to see a schematic on this machine. I've serviced a number of 310's, just haven't had to do hyd repairs on one.