Fuel flooding is one of the most common causes of damage on piston rings. In the event of fuel flooding, the oil film on the cylinder wall suffers so significantly that the piston rings rub metal on metal against the cylinder wall and quickly lose radial wall thickness. Metal contact between the piston rings and the cylinder wall (Fig 1) may only occur briefly and in exceptional cases and is not permitted in normal engine operation. The service life of pistons, piston rings and cylinder bores suffer significantly and is drastically shortened. In normal state, the interacting sliding parts are always separated from metal contact by an oil film. Here, the oil film must therefore be thicker than the unevenness on the surfaces of the interacting sliding parts.
Mixed friction leads to significant radial wear on the piston rings and the cylinder surface. This is clearly visible on the two scraping lands of the oil control ring. Fig. 2 shows a new oil control ring and an oil control ring worn through mixed friction. The two scraping lands are completely worn down. The engine the ring comes from suffered from excessive oil consumption. Radial wear such as this, that not only occurs on the oil control rings, can almost always be traced back to fuel flooding.
Further reasons for fuel flooding on diesel engines include.
►Faulty and leaking injection nozzles
►Fault in the fuel injection pump or settings incorrect
►Incorrectly routed and poorly secured injection lines (vibrations)
►Mechanical faults (piston impact on the cylinder head) due to an incorrect piston protrusion dimension caused by reworking on sealing surfaces and the use of cylinder head seals with incorrect thicknesses
►Poor filling due to blocked air filters
►Poor filling due to faulty or worn turbocharger
►Poor filling due to worn or fractured piston rings
►Poor fuel quality (poor self-ignition and incomplete combustion)
