Understanding Breaker Point Ignition Systems

The rotor is fixed to the top of the distributor shaft and revolves around the inside of the distributor, its contact giving each post on the circumference of the distributor cap a shot of electricity as it passes by. The posts have wires attached to them and these lead to the spark plugs that ignite the fuel/air mixture in the cylinder.

The spark has to be timed so that it sets off the gas at the right part of the piston cycle, usually when the piston is near the top of the cylinder. On most engines ignition timing is set by loosening a distributor hold down bolt and rotating the distributor to advance or retard the spark timing. Old-time garage jockeys used to set timing by ear, turning the distributor until the engine sounded "right." Most mechanics use a timing light that takes a signal from a spark plug wire and releases a pulse of light every time the spark plug wire has electricity running through it. The light is aimed at one of the pulleys on the front of the engine and the distributor is rotated until a notch on the pulley lines up with a mark on the pulley guard.

Troubleshooting

Knowing how a breaker point system works puts you in a much better position to repair it when it breaks down. If your engine isn't running and you suspect the ignition system, the first thing to do is look the whole thing over for anything that is obviously wrong, like loose or broken wires.

Push down hard on the boots at the end of the spark plug wires to make sure that they are on securely. Take a glance at the points; if they look corroded replace them. Check the gap between the points (the space formed when the points are at their widest open setting) with a feeler gauge, getting the proper specification for the gap from a repair manual. A typical setting is 0.015- to 0.020-inch. Use a socket and a breaker bar to rotate the engine so that the points are at their widest gap. The gauge, either a wire type or feeler type, should just slide between the points without pushing them apart.

If this doesn't solve the problem, try tracing the entire circuit, starting with the battery. Test the battery with a voltmeter and a hydrometer. You want the battery to read at least 12.6 volts, assuming you have a 12-volt system. If the battery needs to be recharged make sure to use a trickle charger, a charger that runs at no more than 2 amps. High amp chargers can ruin a battery if used often,, something I had to learn the hard way.

Double-check the battery with a hydrometer.

Be sure to wear splash-proof goggles. Each cell should read almost the same as the others. If you get a drastically different reading in one cell you may have a bad battery.