Why is the water well driller underpowered and emitting thick black smoke

Insufficient engine power, uneven speed, exhaust pipe exhaust black smoke phenomenon has two kinds of:

one is a continuous exhaust black smoke; another is intermittent exhaust black smoke, and the engine shaking shock. Engine power and continuous exhaust black smoke, is the engine most cylinders or all cylinders are too much oil supply, fuel and air mixing ratio is out of proportion, combustion, serious lack of oxygen, diesel fuel combustion is incomplete, suspended free carbon with the exhaust gas with the formation of the discharge.

If the exhaust pipe is intermittent black smoke, and accompanied by “muttering” sound, indicating that the individual cylinder combustion is incomplete.

Summarize the reasons as follows