The fuel control on your diesel is very different than all other auto diesels. The pump has a pneumatic governor rather than mechanical.
Common smoking problems arise from the cracking of two different diaphrams. The diaphram in the rear of the injection pump usually also causes idle surging and probably blacker exhaust. It can be checked by removing the red filter at the rear, top of the injection pump. Place your thumb over the opening and if there is a noticable change in idle speed/condition then you have a bad diaphram.
The other diaphram is in the vacuum pump. Its failure causes oil to pass through the diaphram and on to the runner of number one cylinder. This line is as big as ones finger and if originally clear, it will show the black of oil transfer. If its a black line then removing at the intake is an easy way to view.
Bosch Master, ASE Master, L1
33 years MB technician