【正文】 t is under. If we can move the plate that the points are mounted on, or we could change the position of the distributor cam in relation to the gear that drives it, we can alter the timing dynamically to suit the needs of the engine. Ignition Wires These cables are designed to handle 20,000 to more than 50,000 volts, enough voltage to toss you across the room if you were to be exposed to it. The job of the spark plug wires is to get that enormous power to the spark plug without leaking out. Spark plug wires have to endure the heat of a running engine as well as the extreme changes in the weather. In order to do their job, spark plug wires are fairly thick, with most of that thickness devoted to insulation with a very thin conductor running down the center. Eventually, the insulation will succumb to the elements and the heat of the engine and begins to harden, crack, dry out, or otherwise break down. When that happens, they will not be able to deliver the necessary voltage to the spark plug and a misfire will occur. That is what is meant by “Not running on all cylinders”. To correct this problem, the spark plug wires would have to be replaced. Spark plug wires are routed around the engine very carefully. Plastic clips are often used to keep the wires separated so that they do not touch together. This is not always necessary, especially when the wires are new, but as they age, they can begin to leak and crossfire on damp days causing hard starting or a rough running engine. Spark plug wires go from the distributor cap to the spark plugs in a very specific order. This is called the “firing order” and is part of the engine design. Each spark plug must only fire at the end of the pression stroke. Each cylinder has a pression stroke at a different time, so it is important for the individual spark plug wire to be routed to the correct cylinder. For instance, a popular V8 engine firing order is 1, 8, 4, 3, 6, 5, 7, 2. The cylinders are numbered from the front to the rear with cylinder 1 on the frontleft of the engine. So the cylinders on the left side of the engine are numbered 1, 3, 5, 7while the right side are numbered 2, 4, 6, 8. On some engine, the right bank is 1, 2, 3, 4 while the left bank is 5, 6, 7, 8. A repair 5 manual will tell you the correct firing order and cylinder layout for a particular engine. The next thing we need to know is what direction the distributor is rotating in, clockwise or counterclockwise, and which terminal on the distributor caps that 1 cylinder is located. Once we have this information, we can begin routing the spark plug wires. If the wires are installed incorrectly, the engine may backfire, or at the very least, not run on all cylinders. It is very important that the wires are installed correctly. Spark Plugs The ignition system’s sole reason for being is to service the spark plug. It must provide sufficient voltage to jump the gap at the tip of the spark plug and do it at the exact right time, reliably on the order of thousands of times per minute for each spark plug in the engine. The modern spark plug is designed to last many thousands of miles before it requires replacement. These electrical wonders e in many configurations and heat ranges to work properly in a given engine. The heat range of a spark plug dictates whether it will be hot enough to burn off any residue that collects on the tip, but not so hot that it will cause preignition in the engine. Preignition is caused when a spark plug is so hot, that it begins to glow and ignite the fuelair mixture prematurely, before the spark. Most spark plugs contain a resistor to suppress radio interference. The gap on a spark plug is also important and must be set before the spark plug is installed in the engine. If the gap is too wide, there may not be enough voltage to jump the gap, causing a misfire. If the gap is too small, the spark may be inadequate to ignite a lean fuelair mixture also causing a misfire. The Electronic Ignition System This section will describe the main differences between the early point amp。 condenser systems and the newer electronic systems. If you are not familiar with the way an ignition system works in general, I strongly remend that you first read the previous section The Mechanical Ignition System. In the electronic ignition system, the points and condenser were replaced by electronics. On these systems, there were several methods used to replace the points and condenser in order to trigger the coil to fire. One method used a metal wheel with teeth, usually one for each cylinder. This is called an armature. A magic pickup coil senses when a tooth passes and sends a signal to the control module to fire the coil. Other systems used an electric eye with a shutter wheel to send a signal to the electronics that it was time to trigger the coil to fire. These systems still need to have the initial timing adjusted by rotating the distributor housing. The advantage of this system, aside from the fact that it is maintenance free, is that the control module can handle much higher primary voltage than the mechanical point. Voltage can even be stepped up before sending it to the coil, so the coil can create a much hotter spark, on the order of 50,000 volts that is mon with the mechanical systems. These systems only have a single wire from the ignition switch to the coil since a primary resistor is not longer needed. On some vehicles, this control module was mounted inside the