150 Auto Engine Performance and Driveability Copyright by Goodheart-Willcox Co., Inc. Waste Spark Ignition System In a waste spark ignition system, there is one ignition coil for every two cylinders. In this system, a four-cylinder engine has two coils, a six-cylinder engine has three coils, and a V-8 engine has four coils. The coils are often mounted together in a coil pack. See Figure 8-15. Each coil in a waste spark system has two discharge terminals. These terminals are connected to two spark plugs through conventional resistor secondary wires. When the coil fires, the electricity exits one terminal, travels through the plug wire to fire the plug. On the return path to the other coil terminal, the electricity passes through the engine block, to the other spark plug to fire it, and through the other spark plug wire. In this way, the coil fires both plugs at the same time. The coil wires are arranged so the coil fires one plug on the top of the compression stroke and the other plug on the top of the exhaust stroke. The plug firing on the top of the exhaust stroke has no effect on the operation of the engine. Therefore, the arc at this plug is referred to as the waste engine speed. The rotor is installed on the top of the shaft. The lower end of the shaft may drive the oil pump. The shaft contains the rotating part of the trig- gering device. • Triggering device. These devices are discussed above. The stationary parts are mounted on a plate inside of the distributor body. The rotating part is attached to the distributor shaft. In some cases, the rotating part is integral to the shaft. • Cap, rotor, and wires. These parts distribute second- ary voltage to the spark plugs. On some engines, the distributor has no triggering device. In this case, it is only used to distribute the high- voltage electricity to the spark plugs. Distributors were used on all engines until the early 1980s, but have been replaced by various distributorless ignition systems. Distributorless Ignition Systems A distributorless ignition system (DIS) is a type of electronic ignition system used on most vehicles. A distribu- torless ignition system has fewer moving parts and requires less maintenance than a distributor-type system. The DIS uses a triggering device that allows the system to match the firing of the spark plug to the piston compression stroke. Some distributorless ignition systems have a second sensor that monitors camshaft position. A voltage-sensing device is used in some DIS at one of the coils to measure the voltage spike. From the voltage spike, the device can determine whether a plug is firing on the compression or exhaust stroke. The sensor in the triggering device is placed on the engine near a rotating disk installed on the engine crankshaft, camshaft, or crankshaft pulley. The disk has notches, embedded magnets, or a shutter assembly to pro- duce a signal or vary current flow in a sensor assembly. See Figure 8-14. The resulting electrical signal is sent to the ignition control module. This signal allows the ignition control module to determine the position of each piston in the engine. Many engines have more than one crankshaft sensor ring. On these engines, as well as engines having crankshaft and camshaft sensors, the combination of sensor readings is used to determine piston position. The camshaft disk is cast as part of the camshaft, so the engine cannot be mistimed. The camshaft sensor input may also be used to determine engine speed. The speed input is used with other inputs by the ECM to determine the amount of ignition timing advance. The distributorless ignition system uses multiple ignition coils to generate and distribute the high-voltage electricity. There are several types of distributorless ignition systems, including waste spark, integrated direct, coil-near- plug, coil-on-plug, and dual coil-on-plug systems. Figure 8-14. DIS sensors can be pickup coils or Hall-effect switches. The pickup coil is placed near a magnetic strip or notch in a wheel attached to the crankshaft, crankshaft pulley, or camshaft. (Ford) Wheel Sensor Figure 8-15. This DIS coil assembly is used on a four-cylinder engine. It combines two coils into one assembly. Note the four secondary wires. Coil pack