T6020 hydraulic issue

The pump can stay on sometimes on them. Pulling another spool and releasing again usually works.

Video on a John Deere pump but very similar in principle to yours.

I worked with those type of hydraulic circuits for years in industrial applications. We used closed centre type pumps (variable displacement piston). Basically how they work is, the end of the pump internal pistons is mounted on a swashplate. As the angle of the swashplate increases, the pistons move in and out more and so the pump pumps more. The angle of the swashplate is controlled by the pressure that the pump sees at it's outlet. When you open a service valve for example, the pump will try and maintain constant pressure by pumping more and more oil. This is all controlled on the pump via the compensator.

In your case, the pump may be pumping at it's maximum (swashplate at a big angle) and relieving tru an internal relief valve. It's taking a lot of power from the engine to do this and so the tractor feels sluggish.

We were always told to never touch the compensator as it requires expertise and the right equipment to set.

A diagram showing the principle of how it works.