Mercedes Benz Spark Plug Procedures And Precautions

Spark Plug Procedures & Precautions

This essential component was invented about 160 years ago, but is still evolving in terms of design, materials, and service.

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ZUENDKERZE SPARK PLUG BOUGIE D'ALLUMAGE BUJIA DE ENCENDIDO

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Ah, the lowly humble spark plug. At one time it was king of the ignition system (or at least part of the royal court!). If an engine wasn't running properly or misfiring, the go-to in terms of diagnosis always had the spark plugs at the top of the diagnostic charts. They required frequent adjustment and replacement, and fouled easily. Today it's common for some spark plug change intervals to be up to 100,000 miles. This isn't due strictly to the improvements to the spark plugs themselves per se, although there have been many.

plug, so much so that they are often overlooked in terms of maintenance. That is why keeping proper records of service intervals is paramount to making sure they do get changed on time.

The many improvements to the ignition and fuel systems and even the engine's mechanical components themselves have helped to contribute to the longevity of the spark

Older technicians remember the days of ignition contact points, distributors, carburetors and a single coil to fire multiple spark plugs. To the younger techs out there this may seem to be like reading about the ancient Roman Empire! As often as every 3,000 to 7,000 miles the points, condenser, cap and plugs needed to be changed in order to keep the engine running smoothly. Not to mention frequent carburetor adjustments. Ignition contacts sets were a wearable item so as they began to get pitted and the rubbing blocks would wear, ignition voltage would change as well as timing, leading to poor spark which, in turn, would begin to foul the plugs. Carburetors and air intake systems were terribly inefficient compared to modern day systems and were responsible for premature wear and fouling of spark plug electrodes as well.

Early Beginnings

The German inventor Robert Bosch developed the first functioning spark plug in 1901, then received a patent

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the following year. Although the history of spark plugs is traceable to the mid-1800s, it really isn't certain who invented the first one since it was never patented. While others had a hand in developing the spark plug, Herr Bosch was the one to perfect and patent the technology. It is interesting to note that the spark plug itself was in fact only a by-product that Bosch had to manufacture in order to be able to offer a 'complete' ignition system to manufacturers of the time.

When automobile manufacturing was still in its infancy around 1900, car inventor Karl Benz observed that ignition was proving to be carmakers' 'trickiest problem.' Gottlieb Daimler's glow-tube ignition created a constant hazard of fire, and battery-powered ignition systems restricted the range of cars to a few dozen kilometers, since there were as yet no on-board systems like today's alternators to recharge batteries while driving. Enter the Magneto.

Two engineers for the Bosch Company, Arnold Zähringer and Gottlob Honold, after much trial and error developed the high-voltage magneto ignition system based on what was known as electric-arc ignition. By means of two coils on the armature, it generated a high-voltage current. This current was conducted to a spark plug via a cable connection. The high-voltage current jumped the gap between its electrodes in the form of a spark. As mentioned earlier, some spark plug designs were around since the 1860s or even earlier, however with little success. The main issues were in the design of the insulating material and the electrode. Honold developed a highly insulating ceramic for the insulating body and a heat-resisting alloy for the electrodes. Thus the first direct ancestor of the modern spark plug was born.

Anatomy

A spark plug is made of a center electrode, an insulator, a metal casing or shell, and a side electrode (also called a ground electrode). The center electrode is a thick metal wire that lies lengthwise within the plug and conducts electricity from the ignition cable or coil pack connected to one end of the plug to the electrode gap at the other end. The insulator is a ceramic casing that surrounds much of the center electrode while both the upper and lower portions of the center electrode remain exposed. The metal casing or shell is a hexagon-shaped shell with threads, which allow the spark plug to be installed into a tapped hole in the engine cylinder head. The side electrode is a short, thick wire made from various alloys that is connected to the metal shell and extends toward the center electrode.

The tips of the side and center electrodes are about 0.020 - 0.080 inch apart from each other (depending on the type of engine), creating the gap for the spark to jump across. The basic design has been relatively constant through the years but many advancements have been made in the raw materials used as well as the construction techniques.

According to NGK, a leading manufacturer of spark plugs, ground electrode type spark plugs come in all shapes and sizes. Standard spark plugs typically feature a traditional ground electrode. Ground electrode variations include DFE (double finewire electrode), flat, hybrid, low-angled, multi-

ground, PSPE (projected square platinum electrode), semisurface discharge, slant, square, surface discharge, taper cut, and trapezoid cut, to name just a few.

Double fine-wire electrode (DFE) spark plugs apply a fine wire pin to the ground electrode in addition to a fine-wire center electrode. A smaller electrode requires less voltage to jump the gap, resulting in fewer misfires, which translates to increased fuel economy and horsepower. A smaller electrode also reduces flame quenching. Reducing the electrode size on a standard nickel plug would result in a