[dieselolds]

It’s probably a bad governor cage flex ring within the injection pump.The ring turns black as time and mileage progress which causes the ring to break away in small pieces and causes the return fitting to become restricted.

Another possibility along with a bad flex ring is a stuck servo pin at the bottom passenger side section of the injection pump.These sometimes stick inward and won’t return when the throttle is released.Another area known to cause trouble is the lever on the same side of the pump.They sometimes seize there midway where the pivot point is.

 

[dieselolds]

Here are the prone areas for trouble when it comes down to a rough idle or smoke.

 

[dieselolds]

Thanks for the replies! I think I'll start out as suggested with changing the glow plugs and primary fuel filter as these seem to be easiest and probably overdue anyway. The primary fuel filter has "2013" written on it, guess that doesn't bode well. As far as getting into the injection pump, would it be worth it to check out the lift pump first? Reason I ask about the lift pump is it seems pretty easy to check, but don't know if that could be contributing to my problem or not.

If I do end up getting into the injection pump I assume I'd have to pull it to check these things?

The things I mentioned can be checked without taking the pump off.There’s not much to it once you’ve done it once or twice.

 

[dieselolds]

The thing is continued usage of an injection pump with a bad flex ring will cause the governor cage rivets to be sheared off eventually causing metal grit and carnage to occur inside the pump.The first sign of a rough idle on engines with older early 80s pumps should be investigated asap to prevent further internal damage of the pump especially if the flex ring has failed 100%.