Technical Description for Two Different Audiences

TechnicalDescription for Two Different Audiences

HowSpark Plugs work in Four cylinder Engines

PartOne: Experienced Readers


Sparkplugs are important components in an engine that mechanics, botheducated and amateur, frequently examine when repairing the engine.Essentially, they are insulated plugs that are attached to thecylinder of the internal combustion engine (Hall-Geisler, 2016).Spark plugs play a crucial role in the ignition process by deliveringsparks, which ignite the mixture of air and fuel in the combustionchamber. Improper fitting of the spark plug, damage or any otherfault can lead to serious problems, some of which may require acomplete overhaul of the engine. To this end, it is crucial that carowners and mechanics understand basic and technical aspects of sparkplugs including structure, types, and how they function. This paperdiscusses the structure, working and maintenance issues of sparkplugs. The paper is divided into two parts the first part istechnical and more suitable for experienced readers while the secondpart simplifies concepts for novice readers.

Equipmentand materials needed

Astandard spark plug is made up of three fundamental parts. Theseinclude an insulator, a thread metal pin, and an electrode.Manufacturers use cement or special powder to put together thesethree parts to form an operational leak-proof unit (Beru, 2014). Therole of the insulator is to control the heat levels in the plug,which varies from cold to hot. Hot plugs are convenient for coldengines that experience a lot of stops and start powering. A colderrange plug works better in hot engines that travel continuously forlong distances, especially in hot climatic regions (Insley et al.,2015). The following diagram shows a spark plug



Sparkplugs must be air tighten on the wall of the cylinder using screws. Aspark plug that is too loose can overheat and damage the engine.However, over tightening can result in damage to the threads in thecylinder head.

Often,Spark plug fouling occurs as a result of combustion products, whichare deposited on the plug’s insulator. Accumulation of thesedeposits may lead to failing at great speeds, therefore it isintensified by rich shiftless combinations and unnecessary oil intakethat might sidestep the valve or ring guides. If plugs becomeexcessively hot, the insulator may possibly be spoiled and electrodeswill scorch away fast. In very serious circumstances, hot plugs maypossibly cause untimely burning (also called pre-ignition) of themixture of air and fuel. This decreases power, misuses fuel, andmight destroy the engine especially if carrying a heavy load. Thiswill frequently result in unwarranted scorching of the ground. Thebest heat range for these kinds of plugs is designated based on thedesign of the engine and the functional conditions. Inbroad-spectrum, the plug needs be adequately hot when in use toprevent fouling and sufficiently cool to circumvent pre-ignition andswift wearing away of the electrodes.

Sparkplugs can also be used for diagnostic purposes they show the stateof the engine because it extends into the combustion. Mechanicsobserve removed spark plugs to assess the mechanical state of theengine and possible malfunctions that must be corrected.

Howit works

Sparkplugs are fitted at the top of the cylinder using tight screws. Apiston moves downwards from the cylinder, supplying a mixture of fueland air (see diagram below). Then, the piston moves back up towardsthe spark plug, constricting the combination in the process.Eventually, at what time the piston reaches the Top Dead Center(TDC), the plug triggers and kindles the fuel-air mix (Jerret, 2010).After ignition, the piston is pushed back down to generate power forthe vehicle, then forced back up in order to remove the exhaust, theprocess continues in a circular manner.

Sparkplague in action

Often,the number of spark plugs in the car corresponds to the number ofcylinders in the car, for instance, a four-cylinder car carries fourplugs. In the combustion chamber, spark plugs are influenced by threemain factors – position of the spark, the distance of the spark,and the electrode gap. Basically, the position of the spark refers tothe geometry of its path, the degree to which the path extends intothe combustion chamber (Kadavasal et al., 2015).

Inrelation to the distance of the spark, mechanics are concerned withthree major aspects. First, the distance covered by the air sparkbetween the earth electrode and the central electrode in order toignite the mixture of fuel and air in the combustion chamber. Thesecond aspect is the variable distance of the spark, the path that istaken by the spark if it first goes through the tip of the insulatorbefore going across the earth electrode. Third, the ratio of thedistance covered by the air spark and the variable spark distance,this ratio helps to reduce electrode burn-off thus enabling the sparkplug to have a longer life span.

Part2: Novice Readers

Startingan engine is the first and most crucial process in all machines.Ignition is the process of firing up an engine it can be done eithermanually or automatically. Often, we experience problems whenattempting to start an engine ranging from misfiring, shorts, andsometimes even unresponsive engines. Have you ever wondered whathappens what happens in your engine that causes misfiring? Sparkplugs are the most important engine components in the engine ignitionprocess. This paper presents a step-by-step description of how sparkplugs work.

Theplug has three important parts that enable it to perform itsfunctions – an insulator, an electrode, and a pin (See diagrambelow). Due to the heating that occurs inside the car engine, theinsulator is required to regulate the temperatures. Ideally, thetemperature is determined by how often the engine is ignited, and thedistance covered in one continuous journey. For this reason, coldplugs are used in cars that travel for long distances while hot plugsare used in cars they are ignited more often and cover shortdistances (Insle et al., 2015).

Howit works

Theignition process requires a mixture of fuel and air. The twocomponents are made available in the cylinder through the piston.Rapid movement of the spark plug in the presence of air and fuelcauses the ignition of the fuel-air mixture. The power that drivesthe car after ignition is generated by the backward movement of thepiston, the process happens in circles to sustain vehicle power andcontinuous ignition. The product of the ignition process is thefumes, which are eliminated through the exhaust pipe (Kodavasal etal., 2015).

Misfiringis caused by a fault in the ignition process described above. In mostcases, damages on the spark plug are the sole causes of misfiring.The damages range from broken spark plug pin, worn out spark plug dueto friction, and faulty setting of the fuel-air mixture (Insley,2015).


Giventhe importance of spark plugs in car engines, it is apparent that carmechanics keep maintain them in good conditions. Even withouttechnical knowledge of how to identify faulty spark plugs, thefollowing guidelines can allow car owners and amateur mechanics toidentify faulty plugs and repair them accordingly.

Visualinspection is an easy way of distinguishing between a normalwell-functioning spark plug from a faulty one. Normal spark plugsdemonstrate minimal electrode burn-off and have a white/grayishinsulator base, have correct engine settings and good thermal rating.On the contrary, a visual inspection of faulty spark plugs revealseither one of the following: soot deposits around the insulator tipas well as on the electrode (Jerret, 2010). Often, the soot depositsare because of dirty air filter, incorrect settings of the mixture ora faulty cold start system, resulting in misfiring during cold start.As a solution, it is recommended that you reset the mixture and startsystem, clean up or replace air filters, and install spark plugs withcorrect heat rating. It is importance to seek the services of anexpert whenever you are not certain about how to implement thesecorrective measures.

Anotherway through which faulty spark plugs manifest is through oiled upinsulator tips, and or electrode. In most cases, this gives anindication of excess oil in the combustion chamber or your car couldbe running on a defective turbocharger. This can lead to constantmisfiring, shorting of the spark plugs, and sometimes, completefailure, which may require replacement of the complete engines.Thirdly, faulty spark plugs can manifest through the formation ofglaze (brownish yellow substance) on the insulator tips. Often, theglaze deposits suggest the presence of additives in fuel, duringignition the glaze can liquefy and can conduct electricity. The mosteffective remedy is to replace the plugs (Motortech, 2015)

Finally,broken insulator tip resulting from excessive wear and tear show thatyour vehicle has an engine problem. Insulators tips can also breakdue to incorrect use leading to misfire and ignition challenges.Broken spark plugs must be replaced with new ones (Jerret, 2010).


Theengine is the heart of every vehicle a faulty engine implies thatkey parts, such as spark plugs do not function properly. Obviously,replacing an entire engine is much costly and inconveniencing for carowners. In order to avoid these inconveniences, it is important tofamiliarize with engine components and how they function. This paperdiscussed the spark plug in terms of its structure, types, andworking. Basically, rapid movement of the spark plug in the presenceof aim-fuel mixture causes the ignition. More importantly, it is aprerequisite to maintaining plugs in proper conditions by conductingfrequent checks. Failure to maintain spark plugs in good workingcondition can result in misfiring engines and sometimes completeengine failure.


Beru(2014). All about Spark Plugs. Technical Information No.2. Availablefrom:

Hall-Geisler,K. (2016) How Spark Plugs work. Auto. Retrieved on 2ndSeptember 2016 from:

Insley,J., Kodavasal, J., Chai, X., and Harms, K. (2015). GasolineCompression Ignition: Optimizing start of injection time. Combustionand Flame,162(2):451–461, 2015

Jerret,H. (2010). Spark Plug Operation, Selection, and Maintenance. FarmMachinery Fact Sheet. Utah State University

Kodavasal,J.Lavoie, G., Assanis, N., and Martz, B (2015). The effects ofthermal and compositional stratification on the ignition and durationof homogeneous charge compression ignition combustion. Combustionand Flame,162(2):451–461.

Motortech(2015) Spark Plug: Cleaning Kit Operating Manual. Tools andAccessories: Retrieved from: