MOTORING

Nelson Evening Mail, Volume LXI, 8 June 1927, Page 8

MOTORING

LOOK AFTER THE PLUGS

CHEAP PLUGS ARE DEAR

The heart of the engine, is the epark plug. It if, therefore essential that this part of the engine be of the best .material, and that it be kept in perfect condition. Many faults in tho engine centre at this part. Many troubles in motoring can be corrected by the repair or replacement of the spark plug. A poor grade of plug is poof, econ'ohiv at the start, lioss in power may result through leakage of compression and leakages of electricity. If the body of tho plug is of a poor grade of insulator, it will become porous, and allow tho gas formed under high pressure, to leak through instead of spending its energy on the piston. Or it will allow the electricity needed to ignite the gas to seep through the insulator and leave the. remainder to causo a weak spark. Poor throttling, poor pick-up, missing on hard pulla or high speeds aro often caused by uso of such spark plugs, although other causes may contribute:

A leaky spark plug may bo recognised by'its black appearance, not of tjio kind produced from a layer ' of carbon. ! Spark plug troubles generally arise from leaky piston rings and tho pumping of lubricating oil into tho combustion chambers. They may como from carbon deposits, from cracked porcelain jackets, burned out electrodes, loose plugs, pr either too wide or too narrow a spark gap. . . To avoid most of these troubles, highclass plugs with mica insulators snouTd be selected in the first place, and . the spark gap correctly set with a feeler gauge. Some plug manufacturers recommend a now set of plugs each year, and there is no doubt that with most plugs having porcelain or somo similar composition insulator, this is good advice, but with high-class mica plugs this is certainly not necessary. to locate a missing spark plug, first examine- tho ignition by releasing the wire to each plug, individually, running tlic cngino elowly, and seeing whether epa'rlis are formed when tho wire is placed about three-sixteenths of an inch away from the terminal. If" tho spark appears without a miss, at each spark plug terminal, the ignition isn't at fault. .... To locate life faulty spark plug short each separately, while the engine it tunning, by placing the metal part of a wood-handle screw-driver acrpss terrriinal and engine head. If the engine keeps running as previously .that, plug is the faulty ope. If tho engine misses even more than originally, the spark plug being tested is gobd. '... . .:- .-: The remedy,, bhco the faulty plug is located, ia cither to clean it thoroughly, or replace, it. A spark plug may be' cleaned with kerosene of petrol, better still, acetone. ,In this event, the liquid should be washed off thoroughly, and. the plug be left out to dry before it is replaced. ~ , • , , The insulator should not be scraped for if it 'is porcelain the fine glazed finish is essential to prevent porosity, which causes electrical and gas leaks. _ When the plug, is replaced it should be screwed in firmly, but not so firmly as to crack the porcelain.