Electronic Ignition

One of the things that attracted me to restoring and collecting tractors was the simplicity of the machines themselves. Every part on an old tractor has a function so obvious that even the mechanically uninclined can figure it out. And furthermore the parts are BEEFY, 50 years ago the manufacturers weren't preoccupied with extracting every last penny from the components by making them lighter. Sure parts still break but even then they can typically be repaired with normal equipment you have around the farm, and it doesn't require a laptop computer to diagnose the problem since the culprit is usually laying in the field or lodged in the side of the barn. Because these tractors are so robust, I usually try go back with original parts where possible, avoiding some of the "new and improved" retrofit items. There are however a handful of modern products that are routinely included in my restorations.

Oil, for example has come a long way in the last 50 years and I don't use anything but the latest API grade available. I've heard the arguments for non-detergent oils but would never trade it for today's formulations. Paint is another, the modern acrylic enamels are great for resistance to grease and fuel stains, retaining their shine and they last forever; unlike enamels and lacquers . Still another is the alternator. No doubt using the original generator keeps the tractor pure, but for those of us who use our tractors an alternator is much more consistent and reliable. Yes, I kept my old generator so I can always convert back when one of us retires, i.e. the tractor or me.

I just recently added another product of modern technology that I've allowed into the machine shed. It's electronic ignition. For me electronic ignition always conjured up thoughts of an onboard computer, a wiring harness out of an F-16, and a distributor as big around as coffee can. But I've come across one that puts the electronics only where they need to be and retains all of the other stock components of the ignition system.

It's called the Ignitor, and it's available through our online store. The conversion kit is ingenuously simple as it provides the same switching action as the points but does it electronically. So what makes electronic switching better than points? Well to answer that question you have to take a closer look at how the points actually work. The mechanical operation of the points is really pretty simple: as the distributor shaft rotates, the lobes on the distributor shaft force the contacts of the points open at the exact time spark is needed from the coil and then the rotor directs the spark from the coil to the proper cylinder. (Explanation of the coil's operation is at the end of the article) Now if the electrical operation of the points was this simple, they would likely be as trouble free as gas caps. The problem is, that the points have the difficult job of trying to stop the flow of electricity each time the contacts open. Difficult, because once electricity is flowing in a circuit it doesn't want to stop and in an attempt to keep flowing, it jumps or "arcs" across the contacts. Of course when the points open fully the flow of electricity stops but then a few milliseconds later the points close, the electricity begins to flow, and the whole process starts over again.

If points could survive this whole ordeal and maintain a smooth finish on the contacts everything would be fine. Unfortunately, new points start to deteriorate from the very first time you start the engine. This is because each time the arcing occurs, a microscopic piece of metal is burnt away from the contacts. With this happening several thousand times per minute before long the faces are pitted and the switching action doesn't always happen like it should. The result: Misfire and Hard Starting. Complicating matters more, while the contacts are wearing so is the little piece of plastic that rubs against the distributor shaft. As this wears, the timing and dwell angle change as well. So if this whole chain of events can be avoided by using an electronic switching device, I'm all for it.

Most electronic ignition systems use magnetism to make the system function. When electronic ignition was first introduced, usually a paddle wheel like device was mounted on the distributor shaft that "triggered" a magnetic sensor in the distributor. Several of these systems are still available today, however, they all require a separate control box to make the system work. The Ignitor system is unique in that it uses very strong cobalt based magnets to provide the magnetic field and therefore eliminates the separate control box. Instead of using a paddle wheel, these cobalt magnets (one for each cylinder) are embedded in a sleeve that rotates with the distributor shaft. An electronic sensor is mounted where the points would normally go and as the magnets move past the sensor it is triggered to switch the voltage to the coil. Since the switching is being done electronically, there is nothing to wear and therefore misfire is virtually eliminated. There are other advantages as well: the electronics are totally encapsulated so it's not effected by dirt or moisture and the system will fire no matter how slow the engine is turning while starting.

I found the conversion kit to be very easy to install. On my WD it took about 30 minutes from start to finish. The kit came with everything needed plus a Technical Assistance phone number in case there were any questions. Basically it's just a matter of removing the old points and condenser and installing the Ignitor sensor in their place. The sensor has two wires that need to be routed through a hole in the side of the distributor. My distributor was a Delco which has a small stud on the side where the points and coil wire connect. The stud, insulating washers, and wire that connects to the coil can all be discarded. The two sensor wires can then be pulled through this hole. The magnetic sleeve is then placed over the lobed part of the distributor shaft. At this point the rotor is re-installed and the distributor can be buttoned up. All that is left is connecting the two sensor wires. The black wire simply connects to the minus (-) side of the coil just like the original wire that went to the points. The red wire connects to any "hot" (positive) wire that is controlled by the ignition switch. In my case it was easiest to simply connect to the positive (+) side of the coil. And finally the fun part, fire-'er-up. The old WD sounded good before but now she sounded great!

With all these advantages are there any drawbacks? There is one. You won't be able to pass on to your kids the ritual of "point-gapping" that your dad taught you. Or then again maybe you could keep a spare distributor in the shed just so the young folks know what it was like in the good ole days.

Operation of the Coil

Because the ignition coil has no moving parts, is relatively trouble free, and few people have ever seen the inside of one, it requires a little blind faith to understand its operation. For some people this faith has been quickly restored when they accidentally came in contact with the end of a spark plug wire while the engine was running! Fortunately, you don't have to subject yourself to a 25,000 volt jolt to understand the operation of a coil since the electrical theory is easy to grasp. The coil's job is straightforward, it has to take battery voltage (6 or 12 volts) and increase to a high enough level for the electricity to "jump" the gap in the spark plug. Most coils can produce from 20 to 30 thousand volts although it may not require this much to jump the gap in the spark plug.

A coil can be thought of a somewhat like a transformer that the power company uses to increase (or decrease) voltage. Unlike the power company transformer, the ignition coil is not operating on alternating current (AC), rather it runs on direct current (DC) from the battery. The coil can't really be a transformer because they require AC current, but since the coil only has to provide momentary bursts of high voltage it can be made to act like a transformer. This is done by quickly switching the voltage on and off on the low voltage side of the coil. Coils have a low voltage side, called the primary and a high voltage side called the secondary.

Inside the coil there is lots of wire surrounding an iron rod that goes down the center. When the points close, battery voltage goes to the low voltage side of the coil (through the two threaded studs on each side of the coil) and electrical current "fills" the coil and forms a magnetic field around the iron rod. A split second later, when the points open, the flow of electricity stops abruptly and the magnetic field stops instantly. When this magnetic field stops or "collapeses" it induces a very high voltage in the wire that is on the high voltage side. At this point the high voltage burst looking for someplace to go just like lightning tries to find the tallest tree. The tallest tree in this case is the end of the spark plug and hopefully not the end of your finger. As you can see the coil is at the mercy of the points; if the points provide a good quick switching action the coil can do its job, if not the coil may or may not be able to produce the high voltage and misfire can result.

Note:: Electronic Ignition Kits are in stock and available from Yesterday's Tractor Co. Additional information can found in our store pages or we can be reached by phone at (800) 853-2651.

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