What causes a small single-cylinder diesel engine to run away?

Running away in a small single-cylinder diesel engine refers to the loss of control over the engine speed, which rapidly increases to a level far exceeding the rated speed, accompanied by severe vibrations and abnormal noises. If effective measures are not taken promptly to address this issue, it can lead to connecting rod bolt breakage, damage to the cylinder head, engine block, pistons, and other parts. It can also cause serious accidents such as flywheel breakage, valve and valve spring breakage, and even directly threaten personal safety.

The main causes of diesel engine runaway are roughly as follows: First, a large amount of engine oil enters the cylinder and burns, resulting in excessive diesel fuel supply. Second, there are issues with the governor, where the governor is adjusted to its extreme position.

The causes of diesel engine runaway are:

① Governor flyaway iron detached;

② Governor spring broken;

③ Governor limit screw loose;

④ Fuel injection pump rack stuck at maximum fuel supply position;

⑤ Fuel injection pump rack and tie rod connection loose;

⑥ Fuel injection pump rack and gear meshing position incorrect;

⑦ Excessive oil in wet air filter;

⑧ Excessive oil in oil pan;

⑨ Severe wear of piston and cylinder liner, resulting in excessive oil leakage.

After diesel engine runaway occurs, it is absolutely forbidden to reduce or remove the diesel engine load to avoid a sharp increase in speed. After safely stopping the engine, the cause of runaway should be analyzed and the fault eliminated in a timely manner to prevent runaway from recurring.

Analysis of the causes of runaway in small diesel engines:

(1) Excessive fuel supply

(2) Excessive lubricating oil leakage into the combustion chamber