Running an engine under low loads causes lower cylinder pressures, resulting in ineffective piston ring sealing and poor combustion. This poor combustion will lead to soot deposits which clog and gums piston rings, which causes a further drop in sealing efficiency and exacerbates the initial low pressure. The injectors are likely to have a build-up of carbon that is highly abrasive and could cause bore polishing, which then leads to increased oil consumption and further loss of pressure. Due to the carbon build-up in the injectors, unburnt fuel will leak past the piston rings and contaminates the lubricating oil, causing further deterioration in combustion and heavy smoke from the exhaust.
Internal glazing occurs when hot combustion gases blow past the now poorly sealed piston ring, causing the lubricating oil on the cylinder walls to ‘flash burn’. Once glazing or carbon build-up has occurred, it means that the engine will soon become irreparably damaged and may not start at all. This can only be repaired with a complete engine overhaul, stripping down the engine and re-boring the cylinder bores, cleaning and de-coking combustion chambers, fuel injector nozzles, and valves.




