The Lost Art of Setting Ignition Points
Up until the advent of electronic ignition in the 1970s, if you wanted your car to run correctly, you had to do a little work on it on a regular basis. Now a "tune-up" is essentially extinct, since you don't really need to even change plugs up to 100,000 miles. Part of a car's regular maintenance procedure used to be setting ignition points. Getting it done correctly is something that about 12 people in America still know how to do. Hey, what the hell are points, anyway?
The ignition contact points are essentially a switch for the power flowing from the ignition coil to the spark plugs at perfectly timed intervals. As the distributor turns (good name for a soap opera, BTW), the points open and close thanks to a little lobe on the distributor. A rubbing block rides on that lobe and is attached to a spring-loaded arm. At the end of the arm is one ignition point, and the other is on a stationary mount affixed to a baseplate.
Why do they need to be set?
Every single time the ignition points open and close, high voltage -- tens of thousands of volts, in fact -- flow through their contact. When that contact breaks, it causes a tiny arc. After millions of those tiny arcs, the tungsten contacts wear and get further and further apart. Ignition points need to be set to compensate for that wear, and eventually, they need to be replaced entirely.
How often do they need to be set?
Depends on what kind of driving you do, and what kind of condition the rest of your electrical system is in, but in general, points need to be set every 6,000 miles or so. That's every other oil change, folks. You can't even manage to put air in your tires, for crying out loud. No wonder we came up with a better solution.
OK, cut the attitude. How do you set them?
You need a couple of inexpensive tools to do it, including a screwdriver to remove the distributor cap, a set of feeler gauges, your owner's or service manual, and whatever wrenches/screwdrivers you need to loosen the fixed point.
Obviously, the engine should be off. The points should be in their fully open position. What you're measuring is the gap between the points, the way you would the gap between electrodes on a spark plug. In order to get the points fully open, the engine will probably need to be turned by hand a bit by putting a socket and a breaker bar on the crank pulley and turning it until the points come all the way open.
Then, it's a matter of looking in your manual, figuring out the right gap and inserting the correct feeler gauge blade between the points.
Fold out the gauge that matches the recommendation in the manual, but the gauge one size larger is just as important. You want the correct feeler gauge to insert between the points, and the next size up to not go in. If the next size up goes in, the gap is slightly too wide. If the correct gauge won't slip in without touching, then the gap is too narrow.
Adjust the points by loosening the screw holding the fixed point in place and moving it ever-so-slightly in the proper direction. It's tricky and you'll have to mess with it a little, but you'll get it eventually.
So how come I don't have to do this on my 2013 Ford Focus?
Delco-Remy was testing electronic ignition as early as 1948, and Lucas had a system in 1955 (Ed. Note: Haha haaahaahhhahahaaaaaahahahahahaaaaaaa...Lucas...that's rich...). Pontiac debuted Delcotronic ignition in 1963, and GM had its HEI distributor in all of its cars by the early 1970s, as did pretty much everybody else. These distributors feature a "breakerless" means of flowing high voltage, which typically uses a Hall effect sensor, a transducer that does the work of points without having to actually make contact.
Today, engines use distributorless or direct ignition, which sends low voltage to one coil per cylinder, rather than having a single coil for all cylinders.
If I drive something old, do I have to learn how to do this forever?
Nope. Companies like Pertronix offer a direct replacement for most points ignition setups that replaces the baseplate and the points completely, while maintaining the factory look of a traditional points ignition setup.