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Fig. 68.—Diagram Showing Arrangement of Wiring of a Six Cylinder Engine Having Three Systems of Ignition.
Fig. 69.—Wiring Diagram of Double Ignition System at A, of Triple
Ignition System at B, Both for Four Cylinder Engines.
is connected to the individual coil units. The connections of the magneto system are no different than in the regular dual system previously described, while those of the battery and coil may be easily determined by a close study of the diagram. The primary timer has six contacts, one of which serves each ignition coil. As the firing order of this engine is 1-5-3-6-2-4, the wires from the timer must run to the individual unit coils in the same order so as to have the cylinders fire in proper sequence. For example, the wire from the contact No. 1 of the timer runs to coil No. 1, next in order is contact No. 5, which is wired to coil unit No. 5. Following this comes timer contact No. 3, which supplies current to coil No. 3. While the individual spark coils are connected in order, i.e., coil No. 1 is joined to spark plug and cylinder No. 1, coil
No. 2 to spark plug and cylinder No. 2, and so on the timer contact must be numbered according to the firing order. It will be apparent that two sources of ignition current are provided for the battery and coil systems, one being a storage battery, the other a set of dry cells.
A double ignition system in which a true high tension magneto is used and a four unit vibrator coil and four point timer is shown at A, Fig. 69. This ignition system is for a four-cylinder motor having a firing order of 1-3-4-2. At B, Fig. 69, a triple ignition system for a four-cylinder engine is shown, this being practically the same as that outlined at Fig. 68 except that the wiring diagram is somewhat simpler owing to the lesser number of cylinders. The advantage of a double ignition system is that one can determine if irregular engine operation is due to the ignition system or not very easily by running the engine first on one system, then on the other. If the engine runs as it should on the battery system after it has been misfiring on the magneto it is reasonable to assume that some portion of the magneto system is not functioning properly. If the engine runs well on the magneto, but not on the battery, the trouble may be ascribed to failure in the chemical current producer or its auxiliary devices. On the other hand, if the engine does not run well on either ignition systems, it is fair to assume that the trouble is not due to faulty ignition. A non-technical illustration of one of the double ignition systems that were prominent before the general adoption of self-starters and when the high-tension magneto was not yet accepted without suspicion is shown at Fig. 70.
Battery Ignition System Troubles.-Ignition troubles are usually evidenced by irregular engine action. The motor will not run regularly nor will the explosions follow in even sequence. There may be one cylinder of a multiple cylinder motor that will not function at all, in which case the trouble is purely local, whereas if all the cylinders run irregularly there is some main condition outside of the engine itself that is causing the trouble. The first point to examine is the source of current. Full instructions for the care and repair of storage batteries are given in following pages so we will first consider the simple primary or dry cells. It will be observed that a dry cell is very simple in construction and that nothing is apt to occur that will reduce its capacity except diminution in the strength of the electrolyte or eating away of the zinc can by chemical action. The elements in a dry cell are usually combined in such proportions that about the time the electrolyte is exhausted, the zinc can will also have outlived its usefulness. It is much cheaper to replace dry cells with new ones than to attempt to repair the exhausted ones.
Evaporation of the electrolyte is the main cause of deterioration of dry cells as the internal resistance of the cell increases when
the moisture evaporates. It is said that dry cells will depreciate even when not in use, so it is important for the repairman to buy these only as needed and not to keep a large stock on hand. In order to test the capacity of a dry cell an amperemeter is used as indicated at Fig. 71, B. Amperemeters are made in a variety of forms, some being combined with volt meters. The combination instrument is the best form for the repairman to use as the volts