METHOD AND APPARATUS FOR INSPECTING SPARK PLUG WHILE SPARK PLUG IS INSTALLED IN ENGINE

摘要

Method and apparatus for inspecting a spark plug as installed in an engine, for an abnormal size of a discharge gap and cracking of porcelain, based on a shape parameter value Sn ( = Vn/Tn) calculated from a voltage parameter value Vn which is an average of primary voltage V1 during a period of substantially inductive discharge, and a time parameter value Tn indicative of the period of the substantially inductive discharge. The inspection for the abnormal discharge gap size is effected with the engine held at rest, while the inspection for the porcelain cracking is effected with the engine controlled by a motor so as to increase air pressure within the cylinder bore, contrary to conventional system wherein the inspection is effected during operation of the engine by combustion of an air-fuel mixture.