WHAT IS WRONG?

Sun (Auckland), Volume II, Issue 320, 3 April 1928, Page 7

WHAT IS WRONG?

WHEN THE CAR STOPS. ONE GREAT ADVANTAGE. When an engine stops, contrary to the wishes of the driver, it is a great advantage to know how to set about finding the cause of the failure. Otherwise much time may be lost in futile search and in examination of parts which are in nc way to blame. An experienced driver will, as often as not, know pretty well what is the matter before the car stops, or, at any rate, before he has left his seat to investigate. This comes from experience and a knowledge of the little peculiarities of his car. The man who has this power has passed the novice stage. A mechanical breakage is, of course, unmistakable, and it brings the. car to a standstill most unpleasantly. Usually there is not much chance of setting it right on the road. If an engine suddenly ceases to function simultaneously in all cylinders, it is almost certain that the cause is not in the engine itself, since it is most unlikely that all the cylinders would go wrong at the same moment, nor all the plugs become shorted together. A very sudden loss of power suggests failure of the ignition or a choked jet: a more gradual falling away, accompanied, perhaps, by hissing and some explosions in the silencer, points to a failure m the fuel supply. A modern magneto is not likely to go seriously wrong without warning. If it does, there is nothing for it but to obtain a spare at the nearest garage and leave the faulty instrument to be put right. It may be, however, that the rocker arm of the contact-breaker has stuck on its bearing and does not make contact quickly enough to function properly. The fact that the points are touching when the cover is removed does not prove that they close properly when running. The bearing of the arm is genially a fibre bush and in damp weather this may swell and not work freely. Jt is also possible that the platinum points need attention: they may not be making good contact owing to wear, or not separating the correct distance (.4mm.). or, again, they raav be dirty or pitted. The points should be absolutely flat and meet fairly over their whole surface. The amount of separation should he tested with the gauge provided, and should be the same at every opening. Sometimes a cam may require to be set up a trifle. This should be done in the garage at home rather than upon the road, "if there is apparently nothing wrong with the contactbreaker, the magneto may he tested bv placing a plug on the cylinder head, taking care that the terminal does not touch metal. Turn the engine over by hand or with the electric starter, and watch for a spark between the points. Tn a bright light it is not easy to see the spark, hut the plug may be shaded from the light, so that the spark may be seen. A good spark between the points suggests that there is nothing wrong with the plug or the magneto and its wiring. Tt is, however, not certain proof, because a plug may spark well enough in the open air, but fail to spark through the compressed gas in the cylinder. The width of the cap should therefore be tested and set to what is known to suit the engine best. Some eneine*; run best with a fairly wide gap. others with a small one. In the absence of definite knowledge on this point, try a gap of .02in or .025 in if a magneto is the source of the spark, or ,03in if a col ‘ is used.