What effects can aged/degraded fuels have on the engine of an emergency power system?

The consequences of aging / degradation of a fuel can be severe. The engine will still start and run for a while. However, once the fuel pump delivers deposits and biofilms to the engine, fuel filters and injectors can become blocked, and deposits can build up in fuel lines causing malfunctions and even engine failure. Depending on the extent of the damage, cleaning or replacing the affected components of the engine can incur considerable costs.