Diesel smokes (black smoke)
The first thing you need to pay attention to is the condition of the dust filter, if it is clogged with black soot, disassemble it and throw out the inserts (the filters themselves)

Front suspension - dependent, leaf spring, attached to the frame with elastic hinges.
Guide apparatus and elastic elements - longitudinally located asymmetrical leaf springs

Electrical diagram of the electro-pneumatic door drive ZIL-5301
An electro-pneumatic door closing drive is used on buses and special vehicles. The electrical diagram of the drive is shown below

The oil-moisture separator is designed to clean compressed air from moisture and oil, and to prevent condensate from freezing in air lines and pneumatic drive units.

Adjusting the thrust bearings of the ZIL-5301 steering gear
To adjust the bearings, do the following: