Not sure I understand the problem.
Do you mean the pump will not develop enough pressure
to lift the arms and attachments or do you mean the pump
will not prime (lift hydraulic fluid from its reservoir) ?
I am new to this site, but frequent other allis tractor forums. I have a 1950 allis model C with a Woods RM59 mower. I take care of 3 places with the tractor mowing and bladeing. I have had this tractor for about 4 years she runs strong and has seldom giving me any problems. I hope to do a full restore some day and bring this girl back to her glory days. I have been on alot of tractors and enjoy the allis the most. I have no plans to ever give her up.
I agree with Bear on the pressure gauge, you really need one to do
any real diagnosis on the hydraulic system. If you have one, put it
between the pump discharge and the control valve.
If you don’t have access to a gauge you can try cleaning the by-pass
valve in the control assembly. There is usually a pressure relief / by-pass
valve in the control valve assembly that will limit the cylinder’s exposure
to max pump pressure. This by-pass might be “Stuck” open. You can
remove the slide and spring and make sure they are clean and move freely
in the bore. If you post a pic of the control valve we can probably locate
the access to the by-pass valve for you.
One more thing, does the bucket move? If you tried to move the bucket’s
control into the dump position, will it rotate all the way around.
Starting with the bucket flat on the ground, it should be able to lift the
front of the tractor as it moves into the dump position.
If the bucket’s cylinders seem strong, I don’t think the problem is related
to the pump or the by-pass valve and we should focus on the cylinders for
the arms or the side of the control valve feeding them. If both the arm and
bucket cylinders seem weak, then the problem is either with the pump or
the by-pass valve.
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