Kubota L2500 not getting fuel

I have a Kubota L2500 (600 hours) that will not start now due to a fuel problem. For the past month my wife would tell me the tractor would kill on her but when I would try it later it would start. However the other day when I was cutting grass the power dropped as if fuel was being cut off. It shut off a couple of times, restarted and continued cutting but the same thing happened. This time it started but would only idle no matter how much you pumped the accelerator, then it would not start. Had plenty of fuel, cracked the lines going into the injectors and did not have as much flow as I thought it should have from the first two and had no fuel from the 3rd injector line. I drained the tank and flushed it, put on a new fuel filter, pulled, took apart and cleaned the injectors and the hard line to them and inspected and flushed all hoses on the fuel system. Put everything back and still no start. I took the hard line off the injectors and cranked. The first 2 ports off the injection pump would put out fuel about 1/4" (seemed low but not sure) and the 3rd port would not put out fuel at all. So I am assuming the problem is this pump. Is this a part that is serviceable, maybe has trash that got past the fuel filter plugging it? Or is there something else i am overlooking?

I flushed the tank out by disconnecting the hose off the bottom of the tank that goes to the fuel filter and putting a bucket under it and pouring fresh fuel in. The fuel that came out was clean. The fuel lines seemed to be good with no obstructions but you are right that is the cheapest thing to replace so I will pick up some new lines but shouldn't the injection pump be putting out fuel on all 3 ports and I would think it should be shooting up much higher than 1/4"?

I appreciate the response so far. I did try flushing it again from the tank, through the new fuel filter removing the hose just before the injection pump and everything is clear with no restrictions. I pulled the injection pump and everything looks good as far as I could tell. The rack control arm moves freely and you can feel the springs are operational on the rollers on the bottom. One thing I did notice that I thought was odd is that I blew some air through the injection pump inlet and the only port that air would exit was the 3rd port which is the one that no fuel comes out of. Is there a seal inside the plunger of that port that could have failed? I reinstalled the injection pump and lines and again tried cranking while bleeding air at the injectors. I did get fuel at the first two (although it seemed minimal to me) but none at the third line. I cut open the old fuel filter and it did have some rust internally as well as being dirty. I am thinking it is the pump but still having a hard time believing a 99 model with 600 hours has a bad injection pump. I will check Monday for price of new/rebuilt pump but I know its a costly item as well so I want to be sure. Does this seem like the right approach or am I missing something?

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