The History of Spark Plugs in Early Automobiles

Before dependable electrical ignition, some engines relied on a small burner to heat a tube connected to the combustion chamber. Once the tube became hot enough, it ignited the fuel inside.

By 1917, motorists could choose from dozens of competing spark-plug designs. This American Motorist illustration captures an industry still experimenting with electrode shapes, insulation materials and methods of preventing fouling.

Hot-tube ignition worked on slow-running stationary engines but it became increasingly impractical as automobiles grew faster. The flame had to remain lit and ignition timing was difficult to adjust accurately as engine speed and load changed. Improvements in electrical ignition eventually made the exposed burner obsolete

1907 newspaper report describes British gas-engine operators replacing hot-tube ignition with low-tension magnetos.

Electricity promised a safer, faster and more precise solution.

The challenge was forcing a spark to appear inside a cylinder filled with compressed fuel and air. It had to arrive at exactly the right moment, jump across a tiny gap and repeat the performance thousands of times while surrounded by heat, soot, oil, pressure and vibration.

Today, spark plugs perform this task so reliably that many drivers never see one. Reaching that point took decades of experiments, failures and determined engineering.

Before Electricity Took Over

In 1860, Belgian-French engineer Étienne Lenoir developed a double-acting internal-combustion engine that burned coal gas and used electrical sparks for ignition.

Lenoir’s engine was a converted double-acting steam engine with slide valves to admit the air-fuel mixture and to discharge exhaust products. A two-stroke cycle engine, it used a mixture of coal gas and air.

Lenoir’s engine did not compress its fuel mixture before ignition, so it was inefficient by later standards. Still, it became an important early demonstration of electric ignition and one of the first commercially successful internal-combustion engines. Compression soon changed the problem.

Engine designers discovered that squeezing fuel and air into a smaller space before ignition produced more power. As pressure inside the cylinder rose, however, it became more difficult for electricity to cross the gap between the electrodes.

An ignition system might create a bright spark in open air, then fail completely once installed inside a working engine.

The mechanical engine was becoming stronger. Ignition had to catch up.

Moving the Mechanism Out of the Fire

During the 1890s, Robert Bosch’s workshop began adapting magneto ignition systems for motor vehicles.

Bosch adapted low-voltage magneto ignition to a De Dion-Bouton three-wheeler in 1897. The magneto generated its own electricity, but the system still relied on mechanical contacts operating inside the engine.

A magneto generates electricity mechanically as the engine turns, reducing dependence on early batteries that could weaken or lose their charge.

Gottlob Honold, Bosch’s chief engineer, developed the high-voltage magneto ignition system introduced in 1902. Paired with a fixed-gap spark plug, it allowed the spark to form without moving contacts inside the combustion chamber.

Bosch installed an automotive magneto ignition system on a De Dion-Bouton three-wheeler in 1897. The system was dependable for its time, but it still relied on a mechanical break-spark device inside the engine. Moving contacts and rods had to operate amid heat, pressure, soot and vibration. Those parts wore quickly and limited how fast an engine could run.

Gottlob Honold's breakthrough: The 1902 Bosch high-voltage system. By generating voltage outside the cylinder, it eliminated the need for moving mechanical parts inside the combustion chamber.

Bosch’s chief engineer Gottlob Honold developed the answer.

In 1902, Honold introduced a high-voltage magneto ignition system paired with a spark plug. Rather than producing the spark with moving contacts inside the cylinder, the system generated high voltage outside the combustion chamber and carried it through an insulated wire to a plug with fixed electrodes.

Nothing inside the combustion chamber had to move.

Workers at winding stations, an essential process for Bosch's high-voltage magneto ignition systems.

Nothing inside the combustion chamber had to move. Honold had not invented electrical ignition itself. His achievement was making high-voltage spark ignition practical and dependable enough for fast-running automobiles. Engines could operate at higher speeds, use greater compression and run longer without constant adjustment. Bosch registered the high-voltage system for patent in 1902.

Magnetos Simms Bosch set up its first sales office in Store Street, London, in 1898. A further sales office followed suit in Paris the next year.

The new ignition system soon received a dramatic public demonstration.

In 1903, Belgian driver Camille Jenatzy won the Gordon Bennett Cup in Ireland driving a Mercedes equipped with Bosch ignition. The race subjected the car to rough roads, sustained speed and severe vibration. Jenatzy’s victory helped demonstrate that high-voltage ignition could survive conditions far harsher than ordinary road use.

Camille Jenatzy at the 1903 Gordon Bennett Cup in Ireland. His victory in a Mercedes equipped with Bosch ignition demonstrated that the new system could withstand rain, vibration, rough roads and sustained racing speeds.

Bosch continued using motor racing as a public test of reliability. Period advertisements listed the cars that completed punishing road races using Bosch magnetos and plugs.

The message was simple: if the spark survived a race, it could survive the road.

Bosch continued using motor racing as a public test of reliability. This 1913 advertisement lists competitors that completed a 443.6-mile California road race using Bosch magnetos and spark plugs.

Everyone Had a Better Spark Plug

A 1903 feature in The Beloit Daily Free Press highlighting Carl Lipman’s "Billy Hell" soot-proof spark plug.

Once high-voltage ignition proved practical, spark-plug design became an engineering free-for-all.

Inventors advertised soot-proof plugs, self-cleaning plugs, multi-spark plugs and models that supposedly lasted many times longer than ordinary designs. Their names included Never-Miss, Volcano and the unforgettable Billy Hell.

The advertising was often theatrical, but the problems were real.

Early engines frequently burned fuel unevenly and allowed more oil and carbon into the combustion chamber than modern engines. Early gasoline was inconsistent and lubricating oil could find its way past primitive piston rings, coating the plug with deposits.

Metal points corroded. Porcelain cracked. Electricity escaped along dirty surfaces instead of jumping the intended gap.

A fouled plug could silence an entire cylinder.

Early spark plugs were produced with numerous thread sizes, mounting arrangements and electrode positions. A plug made for one engine might not fit another, even when the two appeared nearly identical.

As automobile production expanded, certain thread sizes and mounting styles became more common. Manufacturers also began organizing their products by engine application, making it easier for garages and motorists to identify the correct replacement.

Factories could manufacture plugs in larger quantities. Garages could stock commonly used models. Application charts could match the correct plug to a particular automobile.

Albert Champion and the Birth of Two Brands

One of the most influential figures in spark-plug history began not as an electrical engineer, but as a bicycle racer.

A vintage advertisement showcasing the legendary partnership between Ford Motor Company and Champion Spark Plugs.

Albert Champion was born in Paris in 1878. After working for a bicycle manufacturer, he became a successful competitive cyclist and later raced motorcycles and automobiles in the United States.

Albert Champion test driving a new two-cylinder Clement Gladiator motorcycle inside the U.S. Customs warehouse in New York after the machine arrived by ship from Paris. The square box on the motorcycle, between the front wheel and the engine, is the gas tank. Note the four-wheel horseless carriage parked in the background.

A serious racing accident helped shift Champion’s attention toward the mechanical side of the new automobile, particularly magnetos, ignition components and spark plugs.

A vintage Champion Spark Plugs counter display cabinet featuring a lineup of early replacement plugs.

In 1905, Champion and his financial backers established the Albert Champion Company in Boston. The company imported French electrical parts and later manufactured spark plugs using ceramic insulators designed to protect the center electrode from moisture, heat and accidental contact with the metal shell.

Champion did not remain with the company that carried his name.

In 1908, automobile entrepreneur William C. Durant recruited him to Flint, Michigan to manufacture ignition parts for Buick. Champion established a new operation, but his former business partners already controlled the Champion name.

The original company moved to Toledo and became Champion Spark Plug. Champion’s Flint operation sold its products under his initials and eventually became AC Spark Plug.

Two of America’s most recognizable spark-plug brands therefore grew from the work of the same French racer.

Major supply relationships with manufacturers including Willys-Overland and Ford helped turn spark-plug production from a small specialty business into a major automotive industry.

Keeping the Spark Alive

Creating a spark was only the beginning.

Engineers also had to prevent electricity from escaping, keep the firing tip clean and stop the plug from cracking under repeated heating and cooling.

Early manufacturers experimented with mica, stone, soapstone and several forms of porcelain. Mica performed well in some racing and aircraft engines, but it could be expensive and difficult to assemble.

Porcelain offered strong electrical insulation and could be manufactured in quantity, but early formulas were often porous or vulnerable to thermal shock. They could absorb oil and soot or crack when a cold engine rapidly reached combustion temperature.

Ceramic specialists gradually developed denser materials that better resisted heat, vibration and electrical leakage.

Proving ground for technology: Bill Holland pilots the Blue Crown Spark Plug Special to victory at the 1949 Indy 500. The car's dominance from 1947–1949 highlighted massive leaps in ceramic insulation, which protected plugs from cracking under extreme racing conditions.

In 1915, the Frenchtown Porcelain Company of New Jersey introduced a composition known as “775” porcelain. Spark-plug histories credit the formula with improved resistance to heat changes and lower oil absorption than many earlier materials.

Manufacturers later incorporated heat-resistant minerals such as sillimanite into ceramic insulators. By the 1930s, researchers were developing compositions rich in aluminum oxide, commonly called alumina.

 Geologist and mineralogist Helen Blair Barlett helped develop alumina-based spark-plug insulators at AC Spark Plug. A patent application filed with her colleagues in 1935 described ceramic compositions designed for greater strength, electrical resistance and resistance to thermal shock.

One of the leading researchers was Helen Blair Barlett, a geologist and mineralogist who worked in the AC Spark Plug ceramic laboratory.

Barlett applied her knowledge of minerals and ceramic structure to the development of stronger electrical insulators. In a patent application filed in 1935,

Barlett and her colleagues described alumina-based spark-plug insulators designed to improve mechanical strength, electrical resistance at high temperatures and resistance to thermal shock. The patent was issued in 1939 and included a claim for an insulator made from recrystallized corundum and cerium oxide.

Her work was part of the broader movement toward alumina ceramics that shaped modern spark-plug insulation.

Even the ribs molded into the upper portion of a spark-plug insulator serve an important purpose. They lengthen the path electricity would have to travel across the outer surface, reducing the risk that current will escape before reaching the electrode gap.

The Spark That Made Motoring Practical

Gottlob Honold’s 1914 U.S. patent for a later electromagnetic sparking device. Filed in 1910, it used a movable center terminal inside the plug and should not be confused with Bosch’s commercially important 1902 high-voltage magneto and fixed-gap spark-plug system.

By the 1930s, the spark plug had evolved from a temperamental experimental device into a dependable, mass-produced automobile component.

High-voltage ignition allowed engines to run faster. Commonly used thread sizes and detailed application charts made replacement plugs easier to find. Improved porcelain and alumina ceramics reduced cracking, fouling and electrical leakage. Advances in manufacturing made each plug more consistent and reliable.

These changes may seem modest compared with the development of the engine itself, but they transformed the experience of owning an automobile. A car that started more easily, continued firing under pressure and traveled farther between repairs was a car ordinary motorists could trust.

The modern spark plug still follows the same basic arrangement established during the early twentieth century: a metal shell, an insulated center electrode and a carefully controlled gap where the spark appears.

Its history is not the story of one inventor creating a perfect device. It is the story of engineers, racers, ceramic specialists and independent inventors solving one weakness after another.