First, if you have a manual, find out what the operating pressure is, or should be. Here is the reason, If your pump is weak and can not get up to the operating pressure, the relief will never come on. If for example, your pump is putting out 2500 psi, then just about anything else on the tractor should be relieved at around 2350 psi. Say, that on your tractor, that is what things should be, then you need to put the gage just off the pump, to see if it is 2500 psi. To check relief pressure, you could put a gage after the valve, in-line with the hose, using a tee and fittings to connect the gage. Activate the valve to lift or lower the bucket to the stops. If the relief valve is working, you should hear, and see the relief pressure on the gage. If the relief is not working, then you could have a leaking valve, or a cylinder bypassing. If a relief valve is leaking, you will not build up enough pressure to get the job done. You can maybe do about half to a third of the tractor capability. If you have a leak somewhere else in the system, that can prevent the pressure build up. You can check the pressure at the PS, or any other valve in the system.
If you were to lose 500 psi, you would lose about 3500 lbs of force on a cylinder capability of 17,671 lbs. You might say, I don't have no where that force, and that would be true, if it were not for the fact that the cylinder is pushing at an angle, and the placement of the lift position on the arms, has a lot to do with the lifting force. That cylinder on a straight push at 2500 psi, is capability of pushing 17,671 lbs. I used a 3 in cyl, at 2500 psi for reference.
