Most classic cars and trucks came with points ignition up until the mid-1970s. They were, and still are, easy to understand and easy to diagnose. While this is called a conventional ignition system, it is something of a misnomer. These are not used on modern cars, at least not in the US. In an electronic system, you still have a distributor, but the points have been replaced with a pickup coil, and there is an electronic ignition control module. Lets discuss the differences between classic car points vs electronic ignition systems.
Points-Conventional Ignition
Conventional: While this is called a “conventional” ignition system, it is something of a misnomer. These are not used on modern cars, at least not in the US. This is an older style of ignition system that uses points, a distributor, and an external coil. They are high maintenance, but easily fixed and cheap. Depending on manufacturer the service intervals can range from every 5,000 to 15,000 miles. For a classic car that gets driven 1,000 miles a year, that is a trouble-free system.
The basic workings are familiar to any car buff. An ignition coil contains a pair of windings around a ferrous core. A set of contact points inside the distributor are open and closed by lobes on distributor shaft as the engine spins. When the points are open, current is sent through the coil’s primary windings, creating an electric field. This sets up a magnetic field in the coil’s ferrous core. When the rotating engine causes the lobes on the distributor shaft to open the points, that current is abruptly shut off, the magnetic field collapses, and that changing magnetic field creates a second much stronger electric field. This causes high-voltage current to flow through the secondary windings, out the coil, and to the center of the distributor cap, where it is carried to the spark plug that the rotor is in contact with. In addition to all that, inside the distributor are springs and weights that conspire to advance the spark—have it fire sooner—as engine RPM increases It really is an ingenious and glorious electromechanical contrivance. It is so good that it’s still with us, at least electrical standard coil works by using exactly the same dual-winding principle. This design does have a fundamental shortcoming. When the points open and close, the electric charge can cause an arc to jump between the point faces. A capacitor (the condenser) is employed to minimize the arcing, but it does not eliminate it. Over time, the arcing across the point faces causes them to pit and burn. This makes the point gap smaller, which in turn increases the “dwell” and decreases the amount of time that the coil must charge up before generating the next spark. A similar problem occurs with the little nylon block that is attached to the points and rides on the distributor’s cam lobes. Over time, the block wears down, which causes the points to not open as far. For both reasons, it is the fate of all points to have their gap get smaller and smaller over time, and eventually reach the, um, point where they do not open far enough to allow the coil to charge for long enough to generate a decent spark. Eventually they close altogether. Or the little nylon block may catastrophically snap off. When either of these things happens, your vintage car dies. If you are lucky, it happens someplace where you can pull over, diagnose the problem, replace the points with a spare set you have in your glovebox, use a matchbook or feeler gauge to re-gap them, and be on your way.
There is another less catastrophic but important problem with the points closing: It changes the ignition timing. For every degree that ignition dwell increases, the ignition timing retards by one or two degrees. Thus, the natural wearing of the point gap causes the timing itself to wear. If the car is just a tool-around cruiser, it is not a huge deal, but if you are vintage-racing the car, or even driving right-foot-down often on the street, the fact that a shrinking point gap retards the ignition timing is a reason to keep the ignition maintained.
And this raises a third problem. The tune-up of a vintage car usually includes replacement of the points and condenser. However, due to globalization, even if you buy the parts at the dealer, you really have no idea where they are coming from and what their quality is.
How do you set points? I am sure most of you reading this already know but let us go through it anyway. It is handy if you have a distributor screwdriver (a screwdriver that will hold a little screw on the end of it). Install your points making sure the base plate is sitting down flat. Most points have a little divet that sticks down past the base plate that needs to go in a hole in the distributor or the points will be off- not good. Once the screw is started just barely snug it. Make sure the rub block is touching or is close to the lobes of the distributor shaft. Now turn the engine over by hand until the rub block is on the highest part of one of the lobes. It does not matter which one. With your screwdriver you will see a notch in the base plate of the points and area of the distributor that has a tit sticking up. Take your screwdriver and put it in between that. By rotating your screwdriver, you can open or close the points. If it does not open or close easy then loosen the screw a tad. With your .016 feeler gauge open the points so you can just slide the gauge through without lifting the rubbing block off the lobe. Once you have it set, tighten the screw, and recheck. Do not crank down on the screw, snug is fine. Now hook the wire up to the condenser and you are good to go. If you are replacing the condensers, make sure you hook it up to the negative side of the coil. If you hook it to the positive side, you will have a point melt down the minute you hit the key.
Points ignition are simple and easy to diagnose. Apparently, some people do not understand simplicity, and replace their points distributor because they were told it was unreliable.
Do not Forget the Condenser.
Points go bad more than condensers, but I have had two condensers fail on me on two different occasions. I would recommend replacing both points and condenser at the same time. (If you really must be “thrifty”, you can probably re-use the condenser if the points were not pitting).
Now let us look at electronic. There are tons of different brands and set ups. I am going to cover the basic one that fits the stock style distributors.
Electronic Ignition
Electronic: An electronic ignition is a modification on the conventional system, and you will find these in widespread use today, although distributor-less systems are now becoming more common. In an electronic system, you still have a distributor, but the points have been replaced with a pickup coil, and there is an electronic ignition control module. These are far less likely to breakdown than conventional systems and provide exceptionally reliable operation. Service intervals on these types of systems are generally recommended every 25,000 miles or so.
Bang for the buck, electronic is a great way to go. A big advantage here is that they usually last a long time. The timing never changes due to points closing. Just install and for most part you are done. If you follow the instructions on how to put them in it is easy. One problem I see here is paying attention to how the wires come out of the distributor. Make sure no internal parts that spin in the distributor are going to rub a hole in the wires. Ok now the Biggy, make sure you read what wire goes where on the coil. Most of the time the red goes to the positive and the black to the negative. Make sure the black wire coming from your car’s ignition switch is on the positive side. If you hook this up wrong in any way there is a good chance, you will fry it the minute your turn the key on. Therein lies one of the disadvantages. I would tell you to carry a spare. Just carry a set of points and condenser in your glove box as a spare. The second disadvantage to electronic ignition is if you leave the key on for any reason without starting the car you can cook it. Example: I was checking my turn signal lights and now my car will not start. Yeah, you cooked it buddy. If you are going to be checking anything electrical with the key on make sure you disconnect the black wire that comes from the ignition switch to the positive side of the coil. Make sure it will not touch metal and then you can turn the key on and do what you want.
Fortunately, there is something you can do about it. When points were superseded by electronic (also called “breaker less”) ignition in the mid-1970s, a star wheel and pickup replaced the points in the distributor sent a reluctance signal to an electronic box that was mounted on the firewall. However, for decades, there have been several small aftermarkets triggering systems that replace the points and condenser and reside completely inside the distributor. While there were optical systems where light from an LED was detected through a rotating slit, it is the magnetic Hall Effect-based systems that have come to dominate the aftermarket.
There are two pieces—a small triggering module that replaces the points and condenser in the distributor via a small adapter plate, and a magnetic sleeve that slides over the lobes and sits under the rotor. There is one magnet inside the sleeve for each of the cylinders. The triggering module senses each magnet as it whizzes by and fires the coil.
Most vintage cars were originally equipped with a ballast resistor in line with the coil. The resistor’s purpose is to be bypassed during starting to provide a stronger spark. Sometimes a prior owner removed the resistor to always provide a stronger spark. Most explicitly states that the total resistance of the coil plus the ballast resistor must be at least 3 ohms. If it is less, the ignition will draw more current than the system is rated for and fry it. Lastly, most documentation also states that if the ignition is left on for more than a short period of time without the engine running, it can pop the unit. This is good advice for any vintage ignition system, as coils are designed to be fired, not to have always-on current.
Some people express concern that if a triggering module dies, it cannot be diagnosed, only replaced. That is not entirely true. Most installing documentation has a procedure to measure the module’s voltage with a multimeter as you move the magnetic ring toward and away from it.
For some quick testing, this trick works on both points and electronic. Grab a test light. If you do not have one get one and keep it in your car. Hook the clip to a ground and put the probe to the positive side of the coil. Have a friend turn the key on. Does the test light, light up? If not, your problem is getting power to the coil and more than likely your distributor parts are fine. If yes, move to the next step. Place the probe on the negative side of the coil. Have your friend try and start the engine. Does the light come on and stay on? If it does, the points might not open, and a reset or new point are in order. If you have electronic then it is cooked. Does the light not come on? This could be coil, or the points are broken off or for some weird reason they opened. If you electronic then again, it is cooked. If the light flashes as the motor is turning over then everything is working fine, and you should be looking for problems elsewhere.
So, there you have it. I prefer electronic to points as they tend to be less maintenance. With that said, I will keep a set of points and condenser with me, just in case I am out on the road and have a problem I do not have to call a tow truck.
So do your own research and make up your own mind. I love not worrying that my points will choose the approach to the highway as the place they will close. And when I see someone else’s vintage car by the side of the road with the hood up, I can still shake my head and say, “It’s always the points.”
- HUGE reduction in maintenance. Points do need to be adjusted every 1000–3000 miles to adjust for rubbing block wear or filed to cut down spikes created by arcing. Most electronic ignition components will last the lifetime of a normal passenger car.
- No separate capacitors (aka condensers) that might fail due to heat (or plain crankiness, since that part should not fail in less than 5 years).
- With electronics you can program the spark event EXACTLY when you want it. Mechanical points offer simple advance curves, through mechanical and vacuum mechanisms. Electronic ignitions give the opportunity to program much more optimal, complex ignition characteristics. Gasoline engines want truly little advance when starting, then a certain amount at idle, then an increasing amount as the rpms build, up to a certain point. Then you want less advance to reduce power above peak, to reduce the chances of the engine killing itself during overrev.
- Electronic ignitions let you (or the manufacturer) easily program different ignition characteristics during cruise for goals like higher gas mileage or lower emissions.
- The system can take inputs from sensors all over the engine and increase or decrease ignition timing according to what is happening right now with the engine, in concert with adjustments to the amount of gas fed in through the injector system. So, if the air filter is clogged, the electronics can reduce the amount of gas being injected into each firing cycle, and if necessary, reduce the ignition timing led to compensate for a rich or lean condition.
- The cost of modern electronics and benefits of tying the ignition in with the rest of modern electronic engine management is relatively cheap compared to the lifetime maintenance cost of doing it with older components and systems. The engine can make more power and live a longer, happier life with the modern stuff.
Some folks do not want to give up points. They want to keep them as part of the electromechanical décor of their vintage car, and I can totally respect that. A good friend of mine was that way, until he had the nylon block snap completely off a new OEM set of points on its first road trip. While he was going 80. His romance with points ended as abruptly as his forward momentum then he started to looking into classic car points vs electronic ignition system. Other folks are worried that a triggering module will affect the stock look of their engine compartment. It is subtle—just a red and a black wire from the distributor to the coil.
