4960 injection pump issue

I have a 4960 that used to start great but now won't start unless it's plugged in or over 50 degrees. The engine blew a head gasket last August after a head bolt snapped. I replaced the gasket and bolts and made sure the liners were good, they had great Cross hatch on them yet and there is no blow by at all. It was starting hard but I thought it was just the blown gasket because after it was replaced it got better for 2 months untill the weather turned. Like all 4k series when it started it would rev up and then settle at idle. It slowly started to loose that and now it won't do that at all it just cranks and cranks and then just idles.
I screwed the aneriod screw all the way in to gain a little more power up top which helped alot. I thought that had something to do with it so I screwed it back out but it didn't help. I'm thinking governor springs next, any ideas?

Post on JD forum. Tim S will know.

Both Bosch and Denso pumps with aneroids have a small hydraulic oil cylinder that cuts in the aneroid after the engine starts, and oil pressure builds up. Pump control rack MUST be fully forward for starting, so the plunger retard start notch is correct location. Engine revs up because a rack hold in magnet is used, most release about 1300-1400 RPM. If engine no longer revs up, either rack is sticking and not pulling fully forward, plungers extremely worn could be the cause. If the pump cam and tappet rollers are breaking down, the shavings will cause rack sticking too.

(quoted from post at 15:27:48 04/02/18) Both Bosch and Denso pumps with aneroids have a small hydraulic oil cylinder that cuts in the aneroid after the engine starts, and oil pressure builds up. Pump control rack MUST be fully forward for starting, so the plunger retard start notch is correct location. Engine revs up because a rack hold in magnet is used, most release about 1300-1400 RPM. If engine no longer revs up, either rack is sticking and not pulling fully forward, plungers extremely worn could be the cause. If the pump cam and tappet rollers are breaking down, the shavings will cause rack sticking too.

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Ok. The tractor runs normally after it starts all though now it won't reach top rpm. Only gets about 300 rpm below top

Ok thanks!

Is the shut off solenoid working correctly, full travel? Maybe low voltage causing the hard start and not completely pulling the linkage to the run position? Watch the travel as somebody else turns the key to on.

(quoted from post at 16:16:50 04/02/18) Is the shut off solenoid working correctly, full travel? Maybe low voltage causing the hard start and not completely pulling the linkage to the run position? Watch the travel as somebody else turns the key to on.

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Yes it's working correctly

Have you replaced fuel filters if the start to plug you can get air in them and it would start hard
and also not speed up all the way . But you should be able to tell that if you try to pull a load .

(quoted from post at 17:27:09 04/02/18) Have you replaced fuel filters if the start to plug you can get air in them and it would start hard
and also not speed up all the way . But you should be able to tell that if you try to pull a load .

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I replaced them last August when it all started

Your injection pump is going bad. When they stop revving up right at startup, they are not going into the start position. There are several things that can cause this but they all are inside the injection pump. IF it where mine I would pull the pump and injectors and have then rebuilt. If you keep running it your going to damage the pump more and maybe the engine too.