IRREGULAR RUNNING

Timaru Herald, Volume CXXXIX, Issue 20077, 6 April 1935, Page 10

IRREGULAR RUNNING

SIMPLE TEST FOR TROUBLE Most drivers are familiar with the symptoms of an engine gradually losing its power, developing at the same time a certain amount of roughness, "Missing” Is the definition usually applied to such a malady; a specific remedy is not always the simple matter which it appears to be on a first investigation. To short-circuit each sparking plug in turn gives some small'-indication as to which is the offending cylinder, or cylinders. A much better idea, however, can be obtained by using two small-link chains, each fitted to a block of wood, to serve as electrical insulators. By dangling the ends of the chains on to the engine, the remaining portions can be draped round the sparking plugs, leaving one only free to spark. In such circumstances the engine can be run on full throttle, and a measure of the efficiency of all cylinders obtained, in addition to "spotting” a delinquent sparking plug. As may be expected, the engine will not run very fast when operating on one cylinder only, and it is quite possible to determine the cylinder which does the least amount of work, even in an engine which is not suffering from “misfiring.” Perhaps a valve tappet requires adjustment, or there may be a bad compression leak caused by a burnt valve seating, whilst a knock or tap from the engine can be located instantly, and if the operator be a little expert in the detection of noise, a heavy thump from a main bearing, the hard knock of a big end or the tap of a piston or gudgeon pin can easily be distinguished when one cylinder only is running under full-load conditions. Even a slack camshaft chain can be detected by running the engine slowly.