BY Larry Carley

To better understand those ignition systems and parts you most often sell to your customers, we need to take a short look back at what has happened to the ignition system over the years. Ignition parts such as spark plugs, plug wires, distributor caps and rotors have been around since the earliest days of the internal combustion engine and have always been high-maintenance, high replacement rate products. But the past couple of decades, the sales of these parts have been hit hard by changes in technology.

The first blow came back on the 1970s when unleaded gas was introduced. Unleaded gas was required by emission regulations because tetraethyl lead in gasoline (used to boost the octane rating of the fuel) was bad for catalytic converters. Up to that point in time, lead was the main reason why spark plugs had to be replaced every 12,000 to 15,000 miles. A build-up of lead deposits on the plugs would eventually cause them to foul and misfire. The change to unleaded fuel doubled ? or even tripled ? the service life of most spark plugs.

In the 1970s and 80s, the nation also experienced a so-called ?energy crisis? that caused fuel prices to soar. The automakers were forced to downsize vehicles and switch to smaller, more fuel-efficient four and six-cylinder engines. Fewer cylinders on the road meant fewer spark plugs needed to be replaced, and lower spark plug sales.

The 1980s arrived, also meant the arrival of computerized engine controls, feedback carburetion, electronic fuel injection and oxygen sensors. Emission regulations required cleaner and leaner running engines. Spark plug gaps were widened to improve ignition reliability and reduce misfires with lean fuel mixtures.

In 1985, a whole new spark plug replacement market was created with the introduction of the first platinum tipped spark plug. By using low wearing platinum for the electrodes, spark plug wear was drastically reduced so spark plugs could last upwards of 100,000 miles. This meant spark plugs did not have to be replaced as often and would provide reliable ignition performance mile after mile. But it also meant fewer spark plugs would ultimately be sold once the vehicle manufacturers began using long life plugs in new vehicles. Today, almost all late model vehicles come factory equipped with some type of long life plugs.

Long-life plugs, which have center electrodes made of wear resistant metals such as platinum or iridium, typically having recommended replacement intervals of 100,000 to 120,000 miles. Plugs with platinum on both the center and ground electrodes (double? platinum plugs) or those with multiple ground electrodes experience even less wear than plugs with a single platinum or platinum-tipped electrodes.

Up until the mid-1980?s, almost all automotive engines used a distributor type ignition system. The distributor distributes the high voltage spark from a single ignition coil to each of the engine?s spark plugs. Attached to terminals on the distributor cap are insulated high-voltage wires that carry the spark to each of the spark plugs. The wires are attached in a specific firing order so the spark arrives at each spark plug just as the piston approaches top dead center on its compression stroke. Inside the cap is a rotor that directs the spark from the cap center terminal to each of the spark plug wire terminals. The rotor is usually gear driven by the camshaft and turns at half engine speed.

The cap and rotor were also maintenance items that had to be replaced because over time, the constant arching of the spark inside the cap caused deposits on the terminal contacts. The cap and or rotor can also develop cracks or carbon tracks that allow the spark to find a shortcut to ground, causing the engine to misfire, die or not start.

To eliminate the cap and rotor as well as wear problems associated with the distributor itself, vehicle manufacturers began introducing various kinds of ?distributor less? ignition systems (DIS). One of the first was GM?s C31 DIS ignition on the 1984 Buick 3.8L Turbo V6. The C31 system used a coil pack consisting of three coils, each of which shared a pair of cylinders opposite each other in the engine?s firing order. The system actually fired both spark plugs simultaneously, but only one ignited the air/fuel mixture because the other fired during the exhaust stroke. This became known, as a ?waste spark? system because one of the two sparks did essentially nothing. A problem in any of the coils in the system would cause two cylinders to misfire. The early C3I system did not have replaceable coils, but later versions did, saving customers the cost of having to replace entire coil packs if only one coil was bad.

In 1988, Oldsmobile came out with its own distributor less system on the 2.3L Quad Four engine called Integrated Direct Ignition (IDI). This system used a separate coil for each cylinder and combines the coils and ignition module into a single assembly that mounted directly top the spark plugs. This also eliminated the need for any spark plug wires on these engines, and improved ignition reliability because there were no plug wires to age or cause problems.

Up until 1980, most vehicles were equipped with carbon core wires (also called distributed resistance wire). This type of construction uses a fiberglass core impregnated with latex graphite. The core typically provides 3,000 to 12,000 ohms per foot resistance to suppress radio frequency interference (RFI). But one of the drawbacks of this design is that internal resistance creates heat. Over time, this ages the carbon core causing resistance to increase. As resistance goes up, so does the risk of ignition misfire. That is why old plug wires are a common cause of poor ignition performance and hard starting.

In the later 1980s, the vehicle manufacturers b began using a different type of ignition wire called ?inductance? or ?mag? wire. This type of wire uses a spiral wound core of copper/nickel alloy. Mag wire offers much less resistance (only about 500ohms/foor) than carbon core suppression wire, and uses the Magnetic field created by the looped wire to block RFI. Mag wire does not change resistance over time, so wire do not have to be replaced as often.

In the 1990s, fuel prices cam back down and Americans decided it was cool to drive large vehicles again. Sport Utility Vehicle (SUV) sales boomed and big, powerful V8s were back. Trucks were soon outselling cars, and that meant more spark plugs that would eventually have to be replaced.

That brings us to today. Fuel prices hit record highs earlier this year but thankfully have come back down to the $2.00 to $2.30 a gallon range in most areas of the country. Even so, automakers are uncertain about the future of big SUVs and fuel thirsty V8s. ?Displacement on Demand? engines such as Chrysler?s 300 Hemi that deactivate cylinders to improve fuel economy when less power is needed allow big V8s to provide good fuel economy and performance ? with no impact on ignition parts one way or the other. There is also a growing demand for hybrid vehicles that combine electric and gasoline power to save fuel. But hybrids still have conventional engines with spark plugs, coils (and plug wires on some), so a growing hybrid vehicle market should also have little or no impact on the sale of ignition parts down the road.

What may have a huge impact on ignition parts sales at some point in the future are fuel cell powered vehicles. The time frame keeps changing, but some say the first mass-produced fuel cell vehicles will be ready in the 2011-?12 model year. The Europeans will likely be the first, with a gradual phase-in among domestic and Asian manufacturers in the years beyond. Even is the technology eventually hits the streets, it will be years before they represent a significant portion of the overall vehicle market.

Okay, so the aftermarket is not selling as many ignition parts as it once did. There is still a strong market for replacement spark plugs and plug wire sets. What?s more, coil sales are starting to climb. Coils are not considered a maintenance item and are fairly reliable. But as the number of vehicles with multi-coil distributor less ignition systems continues to grow, replacements coil sales are expected to grow.

Multi-coil ignitions come in two basic types: Coil-on-Plug (COP) or Coil-Per-Cylinder (CPC) ignition systems and Coil-Near-Plug (CNP) ignition systems. Placing each individual ignition coil directly over its spark plug eliminates the need for long, bulky (and expensive) spark plug wires. This reduces RFI, eliminates potential misfire problems caused by burned, chaffed or loose plug wires, and lowers resistance between coil and plug. Consequently, each coil can be smaller, lighter and use less energy to fire its spark plug.

From a performance standpoint, having a separate coil for each cylinder gives each coil more time to recharge between cylinder firings. With single coil distributor systems, the coil must fire twice every revolution of the crankshaft in a four -cylinder engine, and four times in a V8. With multi-coil systems, each coil only has to fire every other revolution of the crankshaft. This pro vides more saturation time for a hotter spark, especially at higher RPM when firing times are greatly reduced. The result is fewer misfires, cleaner combustion and better fuel economy.

According to the original equipment suppliers that make multi-coil ignition systems, having a separate coil for each cylinder also improves the engine?s ability to handle more exhaust gas recirculation to reduce oxides of nitrogen emissions (important with today?s low-emission vehicle standards). A hotter spark also makes spark plugs more resistant to fouling and helps 100,000mile plugs go the distance. Multi-coil ignition systems also improve idle stability and idle emissions.

On Chrysler, Toyota and many other imports, the COP coils are mounted directly over the spark plugs. Many of these are the thin ?pencil? style coils that extend down into recessed wells in thee engine?s valve covers. On other applications, such as GM?s 2.3L Quad Four, the individual coils are mounted in a cassette or carrier that positions the coils over the spark plugs.

On late-model Corvette, Camaro and other V8s, a Coil-Near-Package (CNP) setup is used because the spark plugs are on the side of the cylinder head. There isn?t room to mount coils over each plug. So the coils are mounted on the valve covers and attached to the plugs by short plug wires.

On most older DIS ignition systems, an electronic module is part of the coil pack assembly and controls the switching of the coils on and off. On most newer DIS systems, the switching function is handled by the ?Powertrain Control Module? (PCM), though there may be some additional electronics and diodes built into the top of each coil. The PCM receives a basic timing signal from a ?crankshaft position sensor? (CKP and sometimes a ?camshaft position sensor? (CMP) to determine engine speed, firing order and timing. The PCM then looks at inputs from the throttle position sensor, airflow sensor, coolant sensor, MAP sensor and even the transmission to determine how much timing advance to give each plug. Most of today?s multi-coil ignition systems are capable of making timing adjustments between cylinder firings, which makes these systems very responsive and quick to adapt to changing engine loads and driving conditions.

On 1996 and newer vehicles, the OBD II system should detect coil problems, as well as ignition misfires. If there?s a problem, the Malfunction Indicator Lamp will come on, and there will be one more Diagnostic Trouble Codes set in the PCM?s memory. These can be read with a scan tool or code reader to diagnose the fault.

If a coil needs to be replaced, make sure the new coil is the same type as the original and has the same primary resistance. Using the wrong coil may damage other ignition components or cause the new coil to fail.

If an engine is experiencing repeated coil failures, the coil may be working too hard. The underlying cause is usually high secondary resistance (bad spark plug wire or spark plugs0, or in some case a lean fuel condition (dirty injectors, vacuum leak or leaky EGR valve).

Future coil problems can often be avoided by cleaning the connectors and terminals when the new coil is installed. Corrosion can cause intermittent operation and loss of continuity, which may contribute to component failure. Applying dielectric grease to these connections can help prevent corrosion and assure a good connection.

On high-mileage engines with distributors or DIS ignition systems, the spark plug wires should also be replaced following a coil failure to assure a good hot spark.