Yanmar 2210

I am working on a yanmar 2210. This is my father in laws tractor and while using it I noticed it's almost impossible to get started then it runs terrible. Will not idle and not very much power. Started trying to see if it was getting fuel and only getting fuel to one injector. This is a 2cyl, not sure of the model. I checked filter, bled everything, removed injector line fittings and pistons from injection pump and Cleaned. I am getting gravity flow from both lines but whenever I turn over you can feel the forward line making pressure and see it spraying but nothing on the rear. The plunger is moving but no pressure is being made. Any ideas on this? Do these pistons wear and quit making pressure or is their something else? Thanks and sorry for the long post.