IGNITION SYSTEM

Hawera Star, Volume LII, 3 September 1932, Page 12

IGNITION SYSTEM

DEALING WITH FAULTS

FREQUENT CAUSES OF TROUBLE.

It sometimes happens that although an engine has been well overhauled and decarbonised, and its valves ground in, the car still refuses to give-as gooo acceleration and petrol mileage as formerly, and the owner becomes perplexed in his search for a -remedy ; of the trouble. In such cases it is wise to sit in judgment on the ignition system, for although it may not have broken down completely, its state of electrical health may be far below par, and no amount of tinkering with the carburettor will secured the ■ improved results desired. Most- owner-drivers are familiar with the more common faults of the ignition, but when it is suspected that something is amiss in that quarter the best course is to make a progressive examination, which, if carried out faithfully, will inevitably reveal the seat of the trouble. Irregular running and “missing” may arise from a defective spark plug, or a partial breakdown of the high tension insulation. It is easy enough to cheek these matters, always bearing in mind that when the spark" at the plug points is tested in the open air it should be particularlv brisk and “fat,” since the resistance which the. high voltage current has to overcome is increased when the plug is in position in the cylinder- and its points are surrounded by a highly compressed mixture. Those motorists who seek to get the best results from their cars are well advised to renew the plugs after every 10,000 miles running, or as soon as their insulating cores show signs of heavy fouling. It is also prudent to replace the high tension leads > at the' same time, as even with partially perished rubber there may be an appreci- j able leakage of the ignition current. The make-and-break is another part, of the ignition equipment which often | gives trouble. If there is rapid pit-, ting of the contact points one should j have the condenser tested, as this, symptom Suggests heavy sparking duel to the failure of that unity. More, often the contact points are at fault, I because their surfaces are not clean,, in the electrical sense, so that there is an excessive resistance to the passage of the low voltage primary current. This may lead to hard starting , and a poor spark, which hinders good petrol mileage and smooth and quick acceleration. . ' . A simple method of testing for this trouble in the case of battery and corl ignition is to note the ammeter reading when the ignition is switched on, | having ascertained beforehand that the . contact points of the make-and-break j are in the closed position. If the dis-v charge recorded is below normal, and is increased when th© fixed and movable contact arms are short-circuited with a clean penknife blade or screwdriver. it is obvious that there is abnormal resistance in the points themselves, and they should be dressed with a magneto file or fine glass paper. After dressing the points, wipe them with a noil-fluffy rag which lias been moistened with petrol, so as to remove all traces of grit or oil. But it does not follow that because, there is an adequate current flowing through the # primary circuit of the battery and coil ignition system, and} the high tension leads and plugs are in good order, that all is well, cor the secondary winding of the con itseh may be ‘ defective. If there are any doubts on that score, the coil may be tested by connecting it direct to the accumulator, and attaching a short piece of wire to its high-tension terminal, bending the wire until it is about spark-plug-gap distance from some part of the metal work cl the car. Then make and break the primary circuit by touching one of the accumulator leads against one of the primary terminals of the coil; the other, of course, being already firmly connected. If there is a good contact spark it is an indication that the primary winding is in order, and if the secondary is also without fault a bright, spark should occur between the bent wire and the metal of the c-ar at the instant the primary contact is broken. Where it is found that a coil, although net positively defective, will not tlirov. a good spark, it is often worth while substituting a suitable ignition coll of high quality, as the better perform- • rre thus obtained from the engine '-ill frequently outweigh the expenseinvolved