4020 3 pt issues

Have a 4020 that does not want to lift the 3 point hitch. If you have the tractor running and walk behind it, grab the lift arm and pick it up, it will raise after that. Lower the lift arms and it will do the same thing all over again. Any ideas on where to look first?

Where is the L/D control lever setting? If not in "D" put it in "D". Have you ever checked hyd stand-by pressure?

I checked, it is in the D position. We have not checked the charge pressure, I do have gauges, where do I check that at.

Plug a 3000# gauge in the rear breakaway coupler and activate the control lever. It should be 2250#s

One thing that every one should realize is some times your standby pressure will weaken a bit at a time un-noticed, then gets down to the near 1750PSI and at that point the priority valve will kick in and limit what little hydraulic pressure that you have to "only" steering and brakes, this is a safety feature built into the mix. Most times the stroke control valve (on the front pump) simply needs turned in a couple rounds to make up for a bit of wear in the spring and seat, and then if that don't do it the stroke valve will need changed. A weak charge pump supply will limit the flow of the main pump but even if it's getting only a little flow it will still hit the 2000PSI, but it will pulse while doing it.. The stand by pressure should be checked at each service time, just to keep you up on what it is. You can easily check it at a remote coupler with a 5,000psi gauge (you should use a gauge with twice the capacity of the system being checked).. But when the pressure dips below 1750psi the SCV's will be dead, so this gives even more reason to keep an eye on it before it gets to that stage,,it can help save a lot of down time later.. Most of us take this for granted, but to the ones that are new to this kind of trouble it will help understand better.

Tim
I guess I'm getting too old(Oldtimers disease)!! Why the need for a gauge that can register "double" the pressure?
Thanks,Jim

It's always been a 'rule of Thumb' ,,having the pressure that you are wanting located in the center of the gauge will give room on the scale for lower as well as higher pressure to be read, plus giving room for a surprise "spike" reading, and giving the gauge room to deal with it.

What's the L/D do?

L/D if adjusted correctly when set in load will automatically sense the load applied by a 3 pt plow to raise/lower plow to keep a constant load on engine. L/D on lever is a less sensitive setting between "L" & "D". "D" should be used for everything except plowing.