3-Point Hitch Motor Stalls when Arms at full height

[RonMar]

I would say that top nut IS the adjustment. That was what drew my attention to mention it to you. By changing the pressure on that spring, you change the relief?

Do you have a pressure gauge? Educate me, is there one or two hydraulic pumps on this machine, or more specifically where does the pressure that powers the 3PH originate at? If it comes from one pump and passes thru the loader hydraulic control valve before comming to the 3PH, Probably the easiest way to measure system pressure is to get a set of quick connects, a high pressure "T" fitting and a gauge, and install that contraption into the hydraulic line that runs to your loader valve from the pump. With this you can also check the loader relief pressure...

 

[rhogg4594]

I don't have a pressure gauge. There is only one hydraulic pump. What I was going to try next was to use some small washers to compress the spring more and monitor the effect. After cleaning out the valve when I tried it before to lift the trailer it managed about six inches before it lost pressure. If there is a difference then we know we are looking in the right area.

I do not have a problem with hydraulic pressure for the 3PH. I have a 350Kg mower which is lifted easily enough. The front end loader lifts well enough but the bucket sometimes tilts down under heavy load when I am trying to raise it. I am not sure whether this might be related or just another problem to be fixed.

 

[RonMar]

Well since the fluid pushes against the spring to relieve, adding washers and spring pressure would I think increase the relief pressure instead of decrease it. Increased pressure beyond limits tends to BLOW THINGS UP so be carefull. Hydraulic injection injuries are very nasty... You really need a gauge inline to determine what is actually happening without doing damage.

The bucket going down is probably due to the lack of load checks in the loader control valve. Load checks are individual check valves built into most modern loader control valves. They only allow fluid to flow in the comanded direction out of the working ports, so if the load on the bucket is greater than the pressure provided by the pump, the bucket dosn't move when commanded up. Bucket in most of it's travel probably dosn't have a lot of mechanical advantage so requires more pressure to perform. If it does this in typical operation, It could indicate that the loader relief is relieving too early. Again, a pressure gauge "T"d into the main line would tell you exactly what is happening... It really is cheap insurance, and would probably cost less than a blown hose or damaged cylinder seal...