Arizona republican., 1921-06-26
|M|SF F|R|NG |S COMMONEST OF
 MOTORS |L[S

One Of the commonest ills to which the internal combustion engine is heir is misfiring. Naturally, this complaint varies in malignancy, sometimes af- flicting only one cylinder, sometimes more, often being merely temporary due to some incorrect adjustment, again being seemingly permanent and calling for drastic action
 Obviously misfiring interferes with the satisfactory operation of the en gine It means that one of more cyl finders are not firing, so that those re maining in operation are carrying on all the work In six-cylnder en- zine missing Is not so annoying as In four. this is obvious, also it is harder to detect In an eight of twelve one of the cylinders may be cut out and the ordinary amateur driver will never detect it Misfiring is more easily detected at low speeds than al hiEh- because the flow of power when the engine is running slowlS tends to become jerky anyway and the jerk caused by a misfiring cyl inder makes detection fairly easy In a general way the basic causes of misfiring may be divided into three classes. those caused by carburetion l failures, those caused by ignition fail l ures and those caused by some de- rang ement of the valve system.
 Misfiring due to csrburetion causes may generally be traced to an inn properly proportioned mixture. the l fuel may be too weak or it may be 1 too strong. The effect will be the same. missing. Under fairly satisfac- l tory conditions of weather if the en- zine, after being warmed up, begins l to misfire it may be assumed that the 1 mixture being fed is either too rich or too lean- That is the first place l to begin trying to correct the trouble | Misfires caused by faulty carburetion will not be confined to any one cyl inder jump to another and make its appearance sporadically in all the cyl inders This is obvious because the I same carburetor feeds the same mix ture to all cylinders
 Two ways of altering the compost ton of the fuel mixture are available one by changing the position of the air control on the dash and the other by feeding more or less gas- In either case the relative strength oi the fuel is altered. When misfirins begins it is good practice to try in creasing the amount of air used Ii | this is the cause of the trouble tho engine will at once take hold again
 On the other hand if the fuel mixture was too weak already the missing vii
 grow worse immediately. which is {
 sign to cut down the quantity of ail
 being fed until the engine begins t'
 function properly. The amount of ali
 should always be just as large as tn
 engine will assimilate.
 It may be that there is some me
 chanical trouble interfering to mak
 the fuel mixture bad. Air leak
 around the inlet manifold or valve
 will allow too much air to enter. Tn
 float of the carburetor may be leak l ing or it may be stuck. the needl
 valve may not be seating properly
 there may be water in the fuel. dir on the needle valve, dirt in the fue or an obstruction in the fuel line. i frequently happens that an engin l may run well enough in low speeds but begins missing as the speed in creases. When the carburetor has tw different adjustments for the differ ent speed ranges the obvious thing | do is to try adjustment of the uppe range In making adjustments of tn carburetor the needle should D moved just a fraction of an inc either way and the engine tried afte each change All adjustments shoul be made while the engine is hot. Misfiring caused by ignition fault is fairly easy to locate because usually is in the same cylinder test a suspected cylinder for ignite misfiring the spark plug is sho = circuited with a screw driver or sim
 lar instrument. When the plug
 shorted, with no difference being n'
 ticed in the operation of the engin
 that cylinder is the guilty one.
 may be that further inspection ms
 show the spark plug at fault; it ma
 be carbonized, the points may be t
 far apart or may be burned, the il
 sulation may be cracked At any ra
 replacement of the plug is the ren
 edy. If the plug is found very oily
 the bottom this may be causing t
 misfiring The oil may have work - it way past faulty piston rings there may simply be too much oil the crank case