The black smoke indicates that it is fueling, possibly too much. Or possibly short of air.
Check that the air filter and air passages are clear of blockages. The air filter may be clogged by fine dust if that is a problem in your area, the passages may have a nest of some sort.
Are you using the glow plugs to start it cold? Or was it still warm from running when this occurred?
Not sure about what you described as loping but that might be a battery problem so if you mean it is struggling to crank the engine you can try cleaning all the ends of the cables (there are four ends to clean), have the battery load tested. It may be something in the starter circuit that is limiting the cranking speed so it struggles to get past the compression point and that is causing the loping.
If you have a decompression knob (which I doubt), use that to get it up to a good cranking speed then give it compression to start.