As Mike D said and or the shaft that is on that housing.
Governor Diaphragm Test
http://www.peachparts.com/shopforum/diesel-discussion/313733-74-240d-grey-smoke-questions.html
Once the Engine is running low pressure in the intake manifold will increase the fuel (remember you have a butterfly valve in the intake). A leak in the Pneumatic Governor Diaphragm decreases the pressure on the Manifold side of the Diaphragm and causes increased fuel.
Another source of black smoke is if the Vacuum Pump Diaphragm ruptures and allows Oil to get up into the intake manifold.
What are the symptoms of a bad IP Governor Diaphragm? Has Symptoms, Cost of Diaphragm, description of how governor works.
http://www.peachparts.com/shopforum/vintage-mercedes/223548-what-symptoms-bad-ip-governor-diaphragm.html
Concerning the Oil in the Fuel Injection Pump. All you can do is fill it properly and see if there is issues (back in the 1970s we used to fill them with 40wt Oil).
The elements are lubed mostly by the Diesel Fuel so there is a good chance they are OK.
It is the Tappets, Rollers, Cam and ball bearings that would suffer from loss of Oil.