MOTOR NOTES.

Putaruru Press, Volume VII, Issue 296, 11 July 1929, Page 7

MOTOR NOTES.

FAULTY RUNNING. WHY THE MOTOR ENGINE “ MISSES.” When an engine “misses, ’> the first thuugiit usually is that there is something wrong witli the distributor, or chat a sparging plug has broken down. Very often tnis proves to be the fact, but on the contrary, many cases of ignition failure are the result of defects elsewhere man in the ignition system. Here ar e a few examples:— Mixture furnished by t carburetter too weak to fire, became o- excessively lean adjustment, dirt in petrol passages, inadequate fuel supply to float clmmuer, water in the petrol, very low grade fuel, carburetter so hot that vapour forms in pctroi passages, too little manifold heat to give good vaporisation. Mixture furnished too rich to fire, caused by excessive fuel fed by the carburetter, running wn- choke closed or vacuum-tank trouble, which lets raw petrol into the intake. Mixture furnished by the carburetter diluted below the inflammable point before the spark occurs, caused by en trance of excess air into the intake passages through leaky carburetter or inlet manifold brar. h connections or worn inlet-valve guides or into the cylinders round loose sparking-plugs, past an mipenect cylinuer-neau gasket, or drawn up from me crankcase past badly fitted piston rings. Weak Mixture. Other causes may be:— M.xture in the cyiii ' - 3 too weak or foui to fire, caused by failure to exhaust vaives to seat and burned gas being drawn in through them instead of fresn mixture, during the suction stroke. Failure of the spark to pass between plug points although the sparking jnergy i s being supplied to the piugs, caused by their internal insulation having become sho -circuited by soot from previous combustions of grossly overrich charges by the conductive residue formed from excess oil which has passed the rings and entered the com bustion spaces by particles of carbon deposits loosened from the combustion space surfaces and caught between their points, or by water reaching them leaks in the gas Short Circuits. Despite these other possibilities however, the cause of ignition trouble is usually to be found in the sparkingor somewhere in the electrical system. the h:gh tension cables running from j the terminals of the distributor cap to the plugs are more likely to fail and interfere with ignition than any other part of the wiring. They carry very high voltage current, capable of escaping through compara‘rV « sll S ht insulation defects, and ot finding its way ’ t 0 earth, without passing through the sparking-plug gaps. When this occurs the engine misses explosions.