Ford 1720 3 point lift problem. I need your HELP!

[J_J]

Okay. We're not too far off from one another.

What would happen if I remove the spring from my relief device?. if I don't provide an artificial resistance to the flow then the pump pumps at some gpm at the pressure the pipe, valves, elbows or whatever else in the circuit develops. As the result flow will be higher at much less pressure developed. Of course we're talking positive displacement pump (gear, screw or diaphragm). I f the pump was centrifugal then I can dead head the pump for a few second without damage to figure out max head developed. As a matter of fact that is how the pump impeller dia is measure without taking the pump apart as part of Test and balance of hydronic system.

jc

If you remove the relief spring from a valve, you now provide an exit point or bleed off orifice, and will never build the pumps max potential pressure.

You need a relief valve in the first valve in the system close to the pump to protect the hyd system.

 

[JC-jetro]

If you remove the relief spring from a valve, you now provide an exit point or bleed off orifice, and will never build the pumps max potential pressure.

You need a relief valve in the first valve in the system close to the pump to protect the hyd system.

That is exactly what I have been trying to say all along. That relief does two functions, set operating pressure and then relives above that set adjustable pressure to protect the pump.

I'm trying to figure out what we're saying that is contradictory

JC,

 

[J_J]

Let me make this clear, the load is what makes pressure the relief only dumps the excess. Very different.

Even though the loader can lift a 1000 lbs and require about 2500 psi to do so, it can operate and develop pressure from 0 to 2495 psi all day with out the relief valve activation.

So in essence the relief valve regulates the over pressure, and the load develops the operating pressure.

If I put a hyd gage in the hyd system, I can observe any pressure any cyl/hyd motor is developing.

If you provide hyd fluid to something, you are providing volume in GPM's, at little or no pressure.

Pressure is developed when the fluid meets some resistance, and if there is no relief, something will break/burst.

Operating can be any pressure up to the relief pressure.

If I am wrong, then I am truly sorry, but I don't think so.

 

[JC-jetro]

Let me make this clear, the load is what makes pressure the relief only dumps the excess. Very different.

Even though the loader can lift a 1000 lbs and require about 2500 psi to do so, it can operate and develop pressure from 0 to 2495 psi all day with out the relief valve activation.

So in essence the relief valve regulates the over pressure, and the load develops the operating pressure.

If I put a hyd gage in the hyd system, I can observe any pressure any cyl/hyd motor is developing.

If you provide hyd fluid to something, you are providing volume in GPM's, at little or no pressure.

Pressure is developed when the fluid meets some resistance, and if there is no relief, something will break/burst.

Operating can be any pressure up to the relief pressure.

If I am wrong, then I am truly sorry, but I don't think so.

I don't thing you're wrong at all. I have the exact same observation. The only thing that I might add or have a slight difference is that in " load develops operating pressure" , not saying your statement is wrong. I can have a dirt scoop dangling in the air and at 1500 rpm and my system develops about 1800 psi. Now if i turn the tractor off with the "static load" in the back and my gauge registers between 300-400 psi or basically weight of the scoop and the pressure it develops on trapped fluid.. Now I take the scoop off and turn the tractor on the pressure I develop is anywhere from 1000 psi to 2150 psi based on the rpm I'm running the tractor. In this case with no load on 3 point the "load" that causes the pressure is relief pressure setting. Now if I raise my lift to max lift where it would cause a slight deadhead and that's when the relief operates and chatters.

In essence engine rpm and relief device spring stiffness sets the operating pressure. Do you disagree?

JC

 

[J_J]

You can't read static pressure unless the gage is teed in the cyl line. When the lever is in neutral, there is no flow.

You will have a static load on any cyl raised even if empty, that includes any metal past the lift point of the cyl.

In order to raise the static load, the pump has to build pump pressure above the static pressure for the cyl to raise more.

Excerpt: You said, In this case with no load on 3 point the "load" that causes the pressure is relief pressure setting.

Not true, the pressure developed in a static system is LOAD only. Even if you start the tractor, and not move the lever, if there is a gage in the cyl circuit, you would see static pressure only.

If I screw the relief valve down all the way down so it never opens, will the circuit develop pressure?

You better say yes. Then what is developing the pressure? LOAD

You said. in essence engine rpm and relief device spring stiffness sets the operating pressure. Do you disagree?


I totally disagree.

Operating pressure is any pressure that makes things work.

 

[JC-jetro]

you can't read static pressure unless the gauge is teed in the cyl line. When the lever is in neutral, there is no flow.

very true. When I tested it i had my gauge attached, with scoop in the air I read about 300-400 psi. I then put a jack stand under the scoop, lowered the scoop and pressure went to zero once all weight was transferred to the jack stand.


You will have a static load on any cyl raised even if empty, that includes any metal past the lift point of the cyl.


Very true, it is the weigh of the arm that rotate the rockshaft, pushing the ram rod against the trapped oil in the lift cylinder

In order to raise the static load, the pump has to build pump pressure above the static pressure for the cyl to raise more.

True, did not say any different.

Excerpt: You said, In this case with no load on 3 point the "load" that causes the pressure is relief pressure setting.


all I'm saying here the weight off the arm or whatever attached to 3 point constitutes the load

Not true, the pressure developed in a static system is LOAD only. Even if you start the tractor, and not move the lever, if there is a gage in the cyl circuit, you would see static pressure only.

very true and that's what I'm saying.


If I screw the relief valve down all the way down so it never opens, will the circuit develop pressure?


You better say yes. Then what is developing the pressure? LOAD

Yes , but that's dead head pressure that will destroy positive emplacement (gear) pump and not centrifugal


You said. in essence engine rpm and relief device spring stiffness sets the operating pressure. Do you disagree?


I totally disagree.

I don't see why you disagree ,I have the gauge on , tractor is on, as I raise the rpm , pressure goes up against the spring spring till it overcomes it and then system protects by reliving.

Operating pressure is any pressure that makes things work

Totally aggree


Well, It might be matter of convension or how we word it. Hate to high jack the thread as all I'm trying to help Gene to get his 3 point running. His pump ios working and he established flow to the hyd cylinder his 3 point will start working. All I suggested to him was to see if there is flow or deduct if there is a seal failure. That's all.

 

[J_J]

JC-jetro ,

One more try.

J_J = If I screw the relief valve down all the way down so it never opens, will the circuit develop pressure?

You better say yes. Then what is developing the pressure? LOAD

JC-jetro = Yes , but that's dead head pressure that will destroy positive emplacement (gear) pump and not centrifugal




J_J = You only have deadhead pressure when the fluid has no place to go, and with a relief valve, there is somewhere the fluid can go. Using a 3000 psi pump system, with relief set at 2500, you can operate anywhere within that pressure, and never trip the relief.

If it takes about 1000 psi to raise half a load, do you think it will take the relief pressure of 2500 psi to raise the load. If the load doesn't develop the pressure, there is no use to talk about deadhead pressure because it will not happen. The relief valve is sitting there waiting on a pressure of 3500 psi.

The only time you will see deadhead pressure is when there is no relief. A relief valve prevents a deadhead pressure.

 

[JC-jetro]

Go it JJ,:thumbsup:

I understand your point. I actually went and looked at the diagram of my pressure relief device. After looking at it closer I realized I can not cause a dead head but only increase the relief setting to the point the spring can no longer be squeezed and whatever relief pressure that would equate to. You are right that the load makes the pressure but it is also a function of engine RPM. If I have a scoop hanging from the back with the gauge attached to the system and as I raise the rpm the system pressure increases given the exact load on the system. Do you agrees with my statement?


JC,

 

[OldBulldogger]

Good news, I found the problem with my hydraulics. First of all, thank you to everyone who contributed to this post and for all the advice. I have learned quite a bit through this process and certainly picked up some great troubleshooting advice along the way. It is great having members on this forum who are willing to help out and share their knowledge.

Over the weekend, I found out that we are expecting 12-15 inches of snow (I live in SE Minnesota) so I ran my tractor into the shop to work on this on-going hydraulic issue of losing my rear hydraulics and 3 point hitch arms. Before digging in, I threw up a quick prayer to the Lord to make this a simple fix and then got started. To those just jumping in,originally I had added a rear single spool remote about two months ago so that I could have hydraulic chute rotation on my 3 pt snowblower. I had used it for several snow clearings and all went well. During the last snowfall however, while blowing snow, I lost hydraulics to the rear and my remote to move the chute quit working as well as my lift on my 3 point arms. I visually checked everything, looked for seepage, broken linkage etc and to no avail found nothing that seemed out of sorts. My front end loader worked but no rear hydraulics. I also observed the hydraulic pump got real hot in the time it took me to get from the road back to shed to park it.

I was convinced I either had a fault in the rear remote spool or that I had blown a seal in the piston cylinder that operates the three point lift. I was just getting ready to do some mechanical diagnosis and I remember that on my diverter block their is a control screw that you can turn to control the three point linkage and another way to control auxilary equipment operation such as a backhoe. See photo: In the manual it describes turning it left for the auxilary equipment and . It has always been set to the left as long as I have owned the tractor. At one time the prior owner had plumbed in lines to run a back hoe which meant hooking up a line when you wanted the backhoe and unhooking it when wanting the loader. I had never messed with it but thought just for kicks, I will turn the control screw to the right (right for the three point linkage) and see what happens. After turning it, I fired up the tractor and low and behold, the three point arms operated. AHA... they do work. I raised them up, and then watched for them to fall thinking I may have a bad piston seal. Nothing happened - they held tight. I then played with the know that controls the rate of drop and it too seemed to work as it should. All was well but then I tried my loader and there was nothing. No pressure at all and the loader would not work. So, I turned the control screw back to the left and AHA... loader works just fine but now no rear hydraulics again. This is odd, the rear obviously works and the front obviously works but independent of each other and no longer at the same time. So now I amd focusing on the diverter block.

I started looking closer at it and then wiggled my hose from the loader spool going into the inlet port on the diverter block. It had a little play at the coupler and seemed a little loose. I tried raising the loader again and this time, hydraulic oil started seeping out of the quick coupler on the hose going into the inlet port. Not good I thought but maybe I getting somewhere I thought. I wiped the coupler clean and wiggled the hose again and in the process I realized the hose was not fully engaged into the coupler. I pulled lightly on it and it came right out. So by this time I am thinking...."could I really be this blessed??? Is this it?" I checked the coupler and found the O-ring to be intact. I quickly cleaned it up and reconnected the hose into the coupler. Gave it a light tug and it held just fine - the coupler is holding as it should. I set the control screw on the diverter block back to the original setting and fired up the tractor and AHA.... everything works again just as it should. The loader worked fine, plenty of pressure to lift the front off the ground with the bucket, and three point had plenty of lift for the blower and it held it up with no settling, and the rear remote operated the chute and as it should. Also, the hydraulic pump did NOT heat up at all. YEEHAW!

What is odd is how the coupler came lose enough to release but did not leak until I wiggled it. I park in the shed with a cement floor so I would have noticed any puddles. Last fall I was clearing some brush in our woods and I guess it is possible a stick or something could have bump the coupler enough to partially release it. The hose going into the intlet port is very stiff so in theory, it could have stayed in put until it got to a point where it finally popped out. Stranger things have happened. All I know is that it is working well now and I did go back out Sunday afternoon and blew snow again for a half hour and all worked just fine. I have attached four photos in this post for those who are interested. The first shows the diverter block with the control screw. The second shows the diverter block with a better view of the inlet hose (black hose on upper left) coming from the loader spool. The last two show the instruction from the owners manual describing the control screw settings on the diverter block.

Thanks again to all! I will provide one final round of updates to let you know how it goes after getting through the winter storm that is upon us today.

 

[JC-jetro]

Wow:thumbsup: That's great news, so the hyd coupler did not attach properly to push the ball check back?

JC,