What is the leading cause of wet stacking in diesel gen-set engines?

Wet stacking occurs when a diesel engine is unable to burn the fuel completely, leading to the accumulation of unburned fuel in the exhaust system and cylinders. This condition is typically caused by operating the engine under too little load, which results in low combustion temperatures. When an engine runs with insufficient load, it may not reach the optimal temperature necessary for complete combustion of the fuel. This incomplete combustion can lead to a buildup of carbon and excess fuel, which combines with moisture from the engine's operation, resulting in wet stacking.

In contrast, operating the engine at too much load can lead to different issues, such as overheating or mechanical stress, but it is less likely to cause the wet stacking condition specifically. Using an improper fuel type can lead to inefficiencies or damage, but it does not solely account for the accumulation of unburned fuel in the same manner as running with too little load. Similarly, faulty injectors can cause performance issues, but they are not the primary cause of wet stacking in the context of load conditions.