Testing for Ignition Trouble.—If the engine misses without regard to speed, test each cylinder separately by short circuiting the plug with a screw driver, allowing a spark to jump. If all cylinders produce a good regular spark the trouble is not with the ignition system.
If any cylinder sparks regularly this will indicate that the ignition system is in working order so far as the unisparker and coil are concerned. The trouble is probably in the high tension wiring between the distributor and plug, or in the plugs themselves. Examine the plugs and wiring carefully. Leaky secondary wiring is frequently the cause of missing and backfiring.
Frequently, when high tension wires are run from the distributor to the spark plugs through a metal tube, trouble is experienced with missing and backfiring, which is due to induction between the various wires in the tube. This is especially likely to happen if the main secondary wire from the distributor to the coil runs through this tube with the spark plug wires.
Whenever possible the distributor wires should be separated by at least one-half inch of space. They should be supported by bracket insulators, rather than run through a tube. In no case should the main distributor wire run through a conduit with other wires.
If irregular sparking is noted at the spark plugs, examine the battery and connections.
If the trouble commences suddenly, it is probably due to a loose connection in the wiring, if gradually, the battery may be weakening or the contact points may require attention.
CHAPTER XXI
PHILBRIN SINGLE SPARK IGNITION SYSTEM
Operation, Adjustment and Care
The Philbrin ignition system consists of a specially designed contact maker and interrupter, a distributor mounted on the same shaft, a nonvibrating heat and moisture proof coil, an armored heat, moisture, and puncture proof condenser, and a special Duplex switch.
Fig. 80. Philbrin Contact Maker—Point Adjustment