John Deere 1120 3pt hitch won't lift when I hook up loa

I have a John Deere 1120 with a model 37 loader.
We have never used the loader before because it was not on when we rebuilt the engine. Just a week ago we were ready to put it on and we hooked up the line to the valve control for the up and down. when we did the drive way needed plowed so when doing so the blade on the 3pt hitch was very slow and delayed. Also with a lot of weight it won't lift it. But I figured out when lifting something you pull or push on one of the loader control levers it lifts just fine. Any Ideas about it?

Welcome to this forum
What you state sounds typical for frt end loader control valve not being configured for closed center hyd system such as your model 1120 has. Simple test disconnect FEL control valve return oil hose from tractor. Cap orifice on tractor where hose was disconnected from tractor. Aim open return hose into open hyd filler hole behind seat. With FEL control lever(s) in neutral then start engine. If oil exits open hose FEL control valve is at fault & needs a ""closed center conversion plug with proper seals"" installed.

Hello James welcome to YT. To add more explanation,
a closed-center system holds full pressure and stops
flow in the supply hose to a valve. When the valve
opens to the cylinder supply hose the fluid flow
begins. A closed-center system requires a special
pump that can stop pumping flow yet maintain
pressure. In an open-center system the fluid is always
flowing through the valve and back to the reservoir. In
an open system when the valve is opened flow is
diverted to flowing to the cylinder supply hose instead
of to the reservoir. When you place an open center
valve in a closed center system you essentially poke a
hole in the dam lowering the pressure and flow that the
3 point is expecting to see. The hole in the dam is the
open center valve allowing the oil to flow back to the
reservoir in the return hose. Hope this make sense.

(reply to post at 18:08:58 03/18/23)

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This makes a bit of sense considering I'm a 13 year that's new to hydraulic systems. But I'm pretty sure it's a closed system because it's always asking for fluid by always sending it back to the reservoir. I did a test and the 3pt hitch works just fine when you disconnect the two lines and plug them. Also I forgot to add the two lines going to the control unit are shaking and vibrating.

(reply to post at 06:11:35 03/19/23)

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sorry correction. I think it's an open center system

On my Kubota 7030 you have to hold the loader remote open for the loader to work. Other remote and 3 pt will not work while the loader
is working, get a bungy cord! You can change the valves and make it an open or closed center or something, but that is above my pay
grade.

This makes a bit of sense considering I'm a 13 year that's new to hydraulic systems. But I'm pretty sure it's a closed system because it's always asking for fluid by always sending it back to the reservoir. I did a test and the 3pt hitch works just fine when you disconnect the two lines and plug them. Also I forgot to add the two lines going to the control unit are shaking and vibrating.[/quote]

JD 1120 has closed-center hyd system. Sounds as if the 2 lines that you disconnected which allowed 3 pt hitch to operate are leading to an opewn-center valve which is incorrect valve for a model 1120

You said ..sorry correction. I think it's an open center
system

That is not correct. The operators manual for your
tractor says on page 33 in a safety warning that your
tractor has a 2250psi ..stand-by.. pressure. The term
..stand-by.. is a direct reference to the pressure held in
a closed-center system against any valve that would
open to use hydraulic flow and pressure. This means
your tractor has a closed-center system as Jim
indicated. As Jim and I said in my our replies your add
on valve needs to be designed as a closed-center
valve or convertible to closed-center comparability.
Another item not mentioned previously is that if the
add on valve has a pressure safety relief valve it needs
to be set just above the tractors actual stand-by
pressure so it does not constantly relieve oil back to
the reservoir.

If you do not have an operators manual you can down
load one from JD for free from the linked page. When
you find your applicable machine type and model click
the arrow pointing sideways so it points down and it
shows the operators manuals and other tech manuals.
Click the arrow to point down by Op manuals there you
can put it in your cart. Also there is a square at the
right with the arrow up to the right corner when you
click that you can view it. The down arrow with the line
under it will down load it to your PC.
JD publications

(reply to post at 14:08:28 03/19/23)

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Thank you so much for this link I just found the model 37 loader owners manual. I was looking at the line hook up and every thing is correct except for the return line. I found out it's in the wrong spot and needs to be moved from the filter area to up to the floor boards. I have to try it when I hook it up but it may fix it.

When you are working on it unhook the pressure line
from the tractor at the add on valve. Open the filler cap
to the rear end where you add oil. Or if you are
changing where the oil returns leave that hose
unhooked. Then use compressed air with a rubber
tipped blower or a rag wrapped on an air tip, blow a
short blast of air in the valve fitting where the pressure
hose was unhooked. If it blows air into the trans
reservoir or out the disconnected return hose your
valve WILL NOT WORK correctly. It is an open center
valve. You need a CLOSED-CENTER valve.