Mohave County miner and our mineral wealth., 1922-10-27
Second Page of the Automobile Section
 Ia

other. Where the misfiring is in the same cylinder all the time, as deter mined by the car the matter is not so difficult because simple shortcir- cutting of the spark plugs in orde, will quickly tell which cylinder it is.
 The average owner is familiar with this method, which consists of holding hammer head against the spark plug and cylinder top while the engine is idling. This cuts out the plug. When it is so shortened it will not produce spark, even if it is not the faulty one. The sense of hearing then is , used to tell one whether the sound o1 the engine changes when a plug is shorted. If there is no change in the sound of engine speed when a certain plug is cut out of action, then that cylinder is misfiring. If, however
 the engine slows down and the mis- firing becomes worse, then that is not the cylinder. One must test all cylinders in this way: S .... ,>.
 The general rule Is that If there is misfiring always in the same cylinder
 suspect ignition or valves, and that if it changes from cylinder to cylinder
 being first in one and then in another, or perhaps two, and SO on, suspect car buretion. These are general rules, which do not hold in many cases.
 Let us suppose that an engine is constantly misfiring in one cylinder. the owner does not know which one, and he is unable to get any clew as to what might be- causing the trouble, The first step is to short the plIgs as mentioned or hold each ignition i cable in turn a small fraction of an inch away from the plug terminal tc note If spark jumps the gap so male. Another method is % remove the sp;rl: plugs, attach the cables and lay the plugs on the cylinder head wni:e the engine is cranked by hard
 Tke plug ends are watched for sparks : The object of all these tests is to determine if there is, it immediately eliminates the whole ignition system i'and one may go to carburetion ol valves. The trouble with these tests is that they do not tell the inex- ,perienced owner if a good spark is being obtained for very often the spark occurs, but it is not strong enough to ignite the charge. Such a condition also may cause perioditie Inisfiring. If the plug insulators are clean at the bottom, not loose or cracked, the electrodes clean and ad. justed to about 1-32 or the thickness of thin dime, one may assume that the spark jumping that gap is good
 If one is not at hand, clean the cleo trodes of the faulty plug. If the in sulator is cracked, there is no use us. ing that plug again. If the insulator is loose, new gasket and tightening of the check nut may remedy the trouble. Carbonizing plug ends is the usual cause of trouble in question. If, however, one of the plugs does not spark and it is replaced with a new one and that one does not spark, then the trouble is in the cable attached to the plug or in the ignition unit. See that the cable ends are clean and tight and that the insulation is not oil soak ed or worn through at any point. Ii the cable is o. K., clean Or dress the breaker contact in the ignition unit and note whether the unit can wobble so as to cause the distributor arm to make poor contact at that segment.
 That is as far as one ought to go in tracing ignition trouble in one par ticular cylinder. If the ignition is O
 K. in any one cylinder and that cylin' der misfires then the valves ought te be suspected. See that they do not stick at all engine speeds, that the tapped clearance is right and that there is not a great deal of oil run. ming down the valve stem guide. The latter causes an air leak; and dilutes the mixture to that cylinder. Any ai, leak to the cylinder will give the same result. Valves that do not seat prop erly may cause nnisfiring, but usually the cylinder is not cut out all the time but only at certain speeds and loads.