Hello Ken and welcome,
A slight amount of moisture can cause the plungers in the pump to rust and to stick. When this happens the rack in the pump also binds and the mixture stays too rich and oil can become saturated with fuel. Any stuck plungers in the pump result in those cylinders getting no fuel at all and the others getting too much.
You can often resolve the problem without a major pump rebuild or without removing the pump from the engine. Remove the injector lines at the injection pump, remove the 19mm fittings on the pump over the stuck plungers. The ball check valves below the fittings are threaded on the outside so you can remove them from the pump. Find a metric fitting to thread over them for removal. After the ball check valves are removed you can look down on top the injection pump plungers and cylinders. Use lots of penetrating oil, and turn the engine. Occassionally tap down on the top of the stuck plungers. If your lucky they will begin to move eventually returning down on their own. It may take some time. Repeat the process as needed. Keep tapping them down as you use the penetrating oil.
The rack in the pump has a opening at the front of the pump. If you remove the small rack cover you will find that the rack is stuck. It will be difficult to move until all the plungers are free. Exercise the rack and the accelerator linkage going to the pump during the process of freeing up the plungers. Eventually everything should begin to free up. After the rack and plungers are free, check the warm up device on the top of the injection pump. A slide valve gets stuck in this device.
During re-assembly make sure to torque the 19mm fittings to 18 ft. lbs. This is critical. You may also wish to add a little two cylce motor oil to your fuel for the next tank or two, to keep things lubed inside the injection pump.
Refer to "injection pump tour" on this site for some insight on the injection pump before you begin. Keep us up to date.
Joe Alexander
Blacklick, Ohio