TESTING SPARKING PLUGS

Manawatu Times, Volume 60, Issue 274, 20 November 1935, Page 13

TESTING SPARKING PLUGS

There arc various methods commonly used when a faulty sparking plug is suspected, but they are not all infallible. For example, if the plug is taken out and laid on the cylinder head it may show a spark when the engine is turned over, but under actual working conditions in the cylinder head, where the plug has to work at almost live times atmospheric pressure, the current may be finding an easier path via a short circuit, or through dampness somewhere in tho ignition system. Even a neou tester will sometimes show a good liash when there is a dead short through tho plug, and there are considerable variations in tho value of the flash. In such cases probably the best method is tho old one of shorting the plugs to the cylinder head one by one with a screwdriver. IL‘ there is no drop in revs, naturally the plug concerned is not doing its 'share of work. Replacement is tho best cure. A CURE POR STICKING VALVES It is not infrequent that a valve tends to stick simply through an accumulation of carbon and congealed oil around the valve stem. It becomes sufficiently.dense to prevent the valve from returning finally to its seating, and, whilst the effect may not bo nociced when driving at a normal cruising speed, tho cylinder is almost sure to cut-out under load. An effective remedy, almost always successful in such eases, is simply to inject into tho air stream of tho carburettor a mixture of petrol anil upper-cylinder lubricant. A fairly liberal dose sent in from a small hand pump or squirt whilst tho engino is revving at about 1000 r.p.m. (onethird throttle opening) will carry the oil into tho offending inlet valve and through! the ports into tho cylinders. Some of the oil' may also bo driven on past tho exhaust valves to help lubricate them.* After this use uppor-oyliuder lubricaut fairly freely with tho petrol, say, 50 per cent, more than that rccommendod, for a period.