MOTORING NOTES

Nelson Evening Mail, Volume LXXI, 24 June 1937, Page 9

MOTORING NOTES

CAR BREAKDOWNS ADVICE ON TWO MAIN CAUSES (By Gerald Ely, London for “The Mail”) It is a tribute to the excellence of modern automobile design that car owners who know little about mechanics should be able to take out on the road a piece of machinery with full confidence that it will convey them to their destination and back home again without any trouble, (that, at any rate, is the experience of the overwhelming majority of motorists. But there is an unlucky minority that does encounter trouble of one sort or another, and it is not always the fault of this minority. I am not among those who put down every mechanical ill to which the motorist is heir, to neglect on his part, for my own fairly long experience of the ownership of different cars has shown me that faulty material and indifferent workmanship do at times creep

No special blame can be reasonably attached to the motor manufacturers when this occurs, for no system of inspection is perfect, and the makers are only too ready to do their best to make good any deficiency in workmanship or material that develops when the car is brought into commission. Moreover, the system of inspection is being constantly improved. For example, an additional method introduced at some works for testing new cars before delivery is to inspect them from underneath. As each car is passed off the road test into the final view department, it is driven over one of a number of new inspection pits. The underneath parts of the chassis and body are illuminated by powerful lamps, and the inspector, who is also equipped with a hand torch, thoroughly examines every visible nut, every oil and water joint, the operation of the hand-brake and all parts where there is the possibility of error. This inspection stage is the final one of a long series which take place at every major point of assembly. But as I have suggested, defects of some kind or other are bound to elude even a lynx-eyed inspector, and the purpose of this article is to draw attention to two main causes of breakdown on the road and to suggest remedial or preventive measures.

IGNITION FAILURE Ignition failure is responsible for the great majority of breakdowns, and this trouble is mainly due to “shorts.” A short-circuit is caused by damage to the insulation which makes the current return to the source otherwise than by resistance, such as a lamp through which it is intended to pass. In other words, the current, instead of going right' along its appointed path, leaks at some point, and takes a short cut back. A “short” may be due to various causes, but the more usual ones are a frayed wire or stray strands of a wire in contact with some metal part. It may also be due to a terminal being loose or faulty, or moisture having congregnted at some point, making an electrical connection. Cracked or porous insulation is another cause.

This explanation of a “short” may be elementary to some readers, but it will at least help to put them on the track of the cause of a sudden breakdown. It is a good plan to carry a roll of insulating tape in the car, so that if the cause of the short-circuit is discovered it can be dealt with by a temporary repair.

But the finding of the cause of a "short” can be extraordinarily difficult, and my advice to new car owners is that they should take preventive measures by examining the wiring system at fairly frequent intervals. They should make sure that insulated wires are well clipped to the frame or body’. To permit wire to hang in festoons is to invite trouble. Never leave a wire in contact with a sharp edge such as the corner of a frame, for it is certain to fray. If there is no other way of dealing with it, \vrap the wire at this point well round with insulating tape.

"SHORTS” IN THE PLUGS Plug trouble is often due to a “short.” The current, instead of giving a spark where it ought to—between the plug points—can jump down from the “top sleeve” of the mica insulation from the terminal to the gland nut of the plug. I am told by the service department of one firm of plug manufacturers that an accumulation of oil, grease, paint, moisture or road dirt on the “top sleeve” of a plug is sufficient to provide an easy path for the current to take, for whatever resistance there may be is frequently of a much lower nature than the resistance at the plug points, so the current takes the line of least resistance and flashes over the “top sleeve.” The “short” can also be internal, and this is usually due to an accumulation of soot, carbon or dirty oil on the internal mica insulation. The oiling and sooting up of plugs can also cause a stoppage on the road, and the best advice that can be given to the new car owner is to make himself familiar with the operation of taking out the plugs and cleaning them, or letting a mechanic do so at intervals. Some service stations like to employ the sand-blast-ing method of cleaning plugs, but the best authorities are against this practice, for it is contended that the sand or other abrasive substance used for cleaning, roughens the surface of the mica, and gives the soot or oil a better hold. Another fairly frequent cause of breakdowns is the presence of dirt of one kind or another in the carburetter. Only the other day I had a hold-up of over one hour in a small car because the engine kept petering out. I found a lot of sawdust in the carburettersome makers use sawdust for cleaning out the petrol tank—but even when this was removed the petrol still refused to come through, and there was nothing for it but to have the car towed to a garage where one of the mechanics applied air pressure through the tank and freed the petrol pipes from obstruction.

LOOKING FOR TROUBLE Every driver should learn to dismantle the carburetter for cleaning. It is really a simple job when you get the knack of it, and any mechanic at the garage which is usually patronised will show how it is done. When the engine begins to splutter and then stops, it is a hundred to one that the carburation is at fault, and the carburetter should be the first component to be investigated. In the majority of cases it will be found that the carburetter float needle has stuck and is preventing the free flow of petrol. It is a simple matter, when you know how, to take down

the float chamber and clean it out. Make certain that the carburetter is all right before blaming the petrol pump where an electrical one is fitted.