DRY RUN FRICTION MARKS DUE TO FUEL FLOODINGTYPICAL DAMAGE APPEARANCE Scoring is typically on one side of the piston (photo at right), and good skirt on other side (photo at left). An originally good skirt bearing panel has narrow, clearly limited longitudinal friction marks superimposed. The ring zone is usually undamaged.  ASSESSMENT Unburned fuel which has condensed on the cylinder walls has locally weakened the oil film such that in narrowly limited strips a dry run occurred between cylinder and piston, which always results in long narrow friction marks. POSSIBLE CAUSES 1) Combustion disturbances due to faults in fuel injection system or carburetor or due to faulty ignition (misfiring). 2) Loss of compression through the valves or cylinder head gasket. 3) Choke too long in operation. |
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