Hi Ron, not sure what "yarning" is, Goggle search came up with many different definitions. I am going to assume it means that the steering is stuck. Also forgot to ask you if tractor is nfe or wfe. For the most part they are the same but I only have experience in wfe so will address that only.
First of all the pump has nothing to do with a seizure, I have worked my 311B for months with the pump laying on the work bench. Steers the same just harder without the power assist.
Check the easiest thing first. Spindles sometimes seize. Pop the tie rod end at the spindle, jack up and see if you can turn the wheel pushing on the tire. If the a spindle has seized it is most likely that the bearing has turned in the bore and the grease hole doesn’t line up with the grease zerk.
On the steering shaft between the steering wheel and the gear box there are only 2 sleeve bearings, 3 U joints, and the Char-lynn. I can’t believe any of them can seize where you can’t break it loose with the steering wheel. Check that by disconnecting the U joint at the gear box.
If the problem is identified above and even if it isn’t you might want to skip the rest of this.
After a seized spindle the most likely culprit is the steering lever in the gear box. The pix is the 311B steering lever, it is splined and pinned to the vertical shaft that passes through the bottom of the gear box and actuates the steering linkages. The pins on top of the lever engage the steering cam (worm gear), part of the horizontal shaft that the U joint on the steering wheel shaft attaches to at the gear box.
The problem is that the pins wear, especially when there is a lack of lube and/or out spec backlash. They can break off, fall under, and jam the steering lever. The steering lever casting can break if there is insufficient back lash also. The steering lever is supported by and slides on the adjuster plug (shown in pix) that is used to set backlash. So now look at the outside bottom of the gear box from the left tire side. On the vertical shaft housing, see that screw about 3/8” with lock nut. That is the lash adjustment. If the steering lever casting breaks it will drop and be lodged on one side of the adjuster plug seizing the steering. If you back that screw out and the adjuster plug drops down, the steering wheel may turn but the steering linkage probably won’t move much, if at all. Bottom line is you have pull the top of the steering gear box.
Just to make your day, following post is a pix of the last one I worked on.