Cold weather running or other causes that prevent the engine from reaching proper operating temperature can cause a buildup of fuel due to incomplete burn that can result in 'wet stacking'. In diesel generators, it is usually because the diesel engine is running at only a small percentage of its rated output. For efficient combustion, a diesel engine should not be run under at least 60 percent of its rated power output.
If an engine fails to reach normal operating temperature due to cold weather or other reasons, it can cause fuel to accumulate and lead to 'wet stacking'. In the context of diesel generators, this often occurs when the engine is running at a reduced capacity. To ensure proper combustion, it's essential that a diesel engine operates within a certain percentage of its maximum potential.