Chapter 8 Ignition System Fundamentals 151 Copyright by Goodheart-Willcox Co., Inc. spark. Since it takes very little voltage to jump the spark plug gap on the exhaust stroke, the coil is powerful enough to fire both plugs. Integrated Direct Ignition System A variation of the waste spark ignition system is the integrated direct ignition system. This system uses conduc- tor strips between the coils and plugs instead of secondary wires. The ignition control module, coils, conductor strips, and spark plug boots are mounted in a single tower unit. The advantage to this system is that the spark plug wires are eliminated. Over time, these wires can cause driveability problems. Also, almost all ignition parts are located in a sealed unit installed onto a cover plate. The only remotely mounted ignition component is the crankshaft position sensor. Coil-near-Plug Ignition System Some distributorless ignition systems use one coil for each spark plug. These systems are commonly called coil- near-plug ignition systems. They use a short secondary wire to connect each coil to its respective plug. See Figure 8-16. Coil-on-Plug (COP) Ignition Systems Many late-model engines are equipped with coil-on- plug (COP) ignition systems. These systems, which are also called direct ignition systems, do not use secondary (spark plug) wires or conductor strips. Instead, the coil assemblies are installed directly over the spark plugs, Figure 8-17. There is one coil assembly for every spark plug. The spark plug boot on the end of the coil assembly prevents arcing and keeps water from entering the coil-to-plug connection. Dual Coil-on-Plug Ignition Systems Some engines have two spark plugs per cylinder to increase combustion efficiency. The dual coil-on-plug ignition system is used on engines with two spark plugs per cylinder. The system has one coil per cylinder. The dif- ference between this system and other COP systems is that each coil is installed directly over one plug and connected to another plug through a secondary wire. The second, or remote, plug fired by the coil is installed in a different cylinder from the first plug fired by the coil. Figure 8-18 shows the coil assemblies installed on an engine. Every coil and plug fires during one crankshaft revo- lution. Each coil fires one plug on the compression stroke and one plug on the exhaust stroke. This reduces the voltage needed to fire the plugs. Depending on the crankshaft posi- tion, the coil fires in one of two ways: • Firing the first plug on the compression stroke and the remote plug on the exhaust stroke. • Firing the remote plug on the compression stroke and the first plug on the exhaust stroke. Figure 8-17. These direct ignition coil assemblies are installed on an inline engine. Coil assemblies Figure 8-18. The dual coil-on-plug system is used on engines with two plugs per cylinder. Coil To remote plug Figure 8-16. The coil-near-plug distributorless ignition system uses one coil per cylinder. Note the short secondary wires, which connect the coils to the spark plugs. Ignition coils Secondary wires