While the primary function of the spark plugs is providing the spark to ignite the air/fuel combination and start the engine, an equally important function of the engine’s spark plugs is to remove heat away from the combustion chamber. Spark plugs act as a heat exchanger, pulling thermal energy away from the combustion chamber and transferring it to the engine’s cooling system.
A spark plug’s heat range is the degree to which it disperses heat. Spark plugs with high heat dispersal are referred to as cold, while plugs with less heat-dissipating characteristics are known as hot.
The structure of the spark plug affects the heat rating:
Found in many passenger vehicles, hot spark plugs have more insulation to transfer the heat slowly, which keeps the temperature high enough to burn off carbon deposits and avoid premature fouling. This helps allow for more time between spark plug changes.
Characteristics of hot spark plugs:
Cold spark plugs are good for high RPM engines and other situations where the engine operates at a high temperature. Because they transfer heat faster, cold spark plugs can get dirty and become fouled sooner because they don’t get hot enough to burn off carbon deposits.
Characteristics of cold spark plugs:
Using the correct heat range is key to getting the performance you want out of your engine. For most vehicles, the manufacturer-recommended spark plug and heat range is the best option. Consult your owner’s manual for the right spark plug for your car.
However, for modified engines, you’ll need to select a spark plug based on the performance you want to achieve with your engine. Keep the following in mind:
For your engine’s spark plugs to work properly, the gap between the center and side electrodes needs to be calibrated perfectly to ensure optimal engine performance. Having the right gap ensures that the arcing occurs at the proper voltage to ignite the fuel and generates the combustion that makes the engine run. When you need to adjust the gap on a spark plug, it’s time to reach for a spark plug gap tool.
Whether you’re looking to maximize the performance of your vehicle or just want to double check that the setting is right, using a spark plug gap tool is vital.
Featuring several metal blades or wires in different thicknesses, a feeler gauge looks like a pocket knife. Each blade or wire is a specific thickness marked in thousandths of an inch (imperial) or millimeters (metric). With a wide variety of blades or wires, you’ll be able to measure almost any gap.
Ideal for use with iridium spark plugs and other plugs containing precious metals, feeler gauges are more accurate than other types. A drawback is the fact that you’ll need a pair of pliers to bend the spark plug electrode since the blades will become deformed if you try using them to adjust the plug.
Named for its coin-like shape, a coin style spark plug gauge features measurements around the edge. The gauge’s outer edge is thin and as you move around the gauge, it gets thicker. This type of gauge is also called a ramp style gauge.
Economical, you can bend the spark plug electrode with this tool but accuracy can be an issue due to the gradual slope of the edge. Good for traditional copper spark plugs, it shouldn’t be used with iridium spark plugs. Using a coin gauge can damage the precious metals in this type of spark plug.
The wire loop style is also shaped like a coin but it has several wire loops of different thicknesses protruding from the edge. As accurate as a feeler gauge, it has a hook to bend the spark plug electrode. A drawback is the limited number of loops, which can make it ineffective for odd gap sizes.
Although there are many different types of ignition systems on the market today, most can be placed in one of the three groups:
An automotive ignition system is divided into two electrical circuits -- the primary and secondary circuits.
The primary circuit carries low voltage. This circuit operates only on battery current and is controlled by the breaker points and the ignition switch. When the ignition key is turned on, a low voltage current from the battery flows through the primary windings of the ignition coil, through the breaker points and back to the battery. This current flow causes a magnetic field to form around the coil.
The secondary circuit consists of the secondary windings in the coil, the high tension lead between the distributor and the coil (commonly called the coil wire) on external coil distributors, the distributor cap, the distributor rotor, the spark plug leads and the spark plugs. As the engine rotates, the distributor shaft cam turns until the high point on the cam causes the breaker points to separate suddenly. Instantaneously, when the points open (separate) current flow stops through the primary windings of the ignition coil. This causes the magnetic field to collapse around the coil. The condenser absorbs the energy and prevents arcing between the points each time they open. This condenser also aids in the rapid collapse of the magnetic field.
The line of flux in the magnetic field cut through the secondary windings of the ignition coil, creating a high voltage - high enough to jump the gaps between the rotor and the distributor cap terminals, and the electrodes at the base of the spark plug. Assuming that the engine is properly timed, the spark reaches the air-fuel mixture in the cylinder and combustion begins.
As the distributor continues to rotate, electrical contact between the rotor and distributor cap terminal is broken, stopping the secondary flow. At the same time, breaker points close to the complete the primary circuit, allowing primary current to flow. This primary current will again create a magnetic field and the cycle is repeated for the next cylinder in the firing order.
Like conventional ignition systems, electronic systems have two circuits: a primary circuit and a secondary circuit. The entire secondary circuit is the same as in a conventional ignition system. In addition, the section of the primary circuit from the battery to the battery terminal at the coil is the same as in a conventional ignition system.
With the ignition switch turned on, primary (battery) current flows from the battery through the ignition switch to the coil primary windings. Primary current is turned on and off by the action of the armature as it revolves past the pickup coil or sensor. As each tooth of the armature nears the pickup coil, it creates a voltage that signals the electronic module to turn off the coil primary current. A timing circuit in the module will turn the current on again after the coil field has collapsed. When the current is off, however, the magnetic field built up in the coil is allowed to collapse, which causes a high voltage in the secondary windings of the coil. It is now operating on the secondary ignition circuit, which is the same as in a conventional ignition system.
The third type of ignition system is the distributorless ignition. The spark plugs are fired directly from the coils. Spark plug timing is controlled by an ignition module and the engine computer. The distributorless ignition system may have one coil per cylinder or one coil for each pair of cylinders.
There are several advantages of not having a distributor:
No timing adjustments.
No distributor cap and rotor.
No moving parts to wear out.
No distributor to accumulate moisture and cause starting problems.
No distributor to drive thus providing less engine drag.
The combination of letters and numbers assigned for every Champion spark plug is a logical formula which indicates the major features of its design.
Resistor - If an R is present, this indicates a resistor type spark plug. Resistor type spark plugs reduce the amount of radio frequency interference (RFI) that can cause ignition misfires and static on the radio.
Shell Design - This refers to the thread size and reach of the spark plug.
Heat Range - The middle number indicates the heat range of the spark plug, the higher the number the hotter the heat range.
Firing End Design - The letters after the heat rating indicates a special spark plug construction feature called the firing end design. The letters refer to the center electrode material, projection dimension and ground material.
Gap Designation - The number after the heat rating indicates the wide gap designation. Please note, the wide gaps are required to meet federal and California requirements.
R Resistor 3k ohm/ 10k ohm
K Resistor 1k-2k ohm
T Resistor 7k-15k ohm
Q Low resistance, inductive suppressor
X Combined resistive/inductive suppression
U Internal auxiliary air gap (booster gap)
THREAD x REACH x SEAT x HEX
A 12mm x 1.25mm, .750", gasket/joint, 5/8" or 18mm
C 14mm x 1.25mm, .750", gasket/joint, 5/8"
CJ 14mm x 1.25mm, .375", gasket/joint, 3/4"
DJ 14mm x 1.25mm, .307", taper, 5/8"
E 14mm x 1.25mm, .984", taper, 5/8"
EA 12mm x 1.25mm, 1.043", gasket/joint, 14mm
EC 14mm x 1.25mm, 1.043", gasket/joint, 5/8"
ER 12mm x 1.25mm, 1.043", gasket/joint, 5/8"
ES 14mm x 1.25mm, .984", taper, 5/8"
ET 12mm x 1.25mm, 1.043", taper, 14mm
F 18mm x 1.5mm, .429", taper, 13/16"
G 10mm x 1.0mm, .750", gasket/joint, 5/8"
J 14mm x 1.25mm, .375", gasket/joint, 13/16"
L 14mm x 1.25mm, .500", gasket/joint, 13/16"
N 14mm x 1.25mm, .750", gasket/joint, 13/16"
P 12mm x 1.25mm, .500", gasket/joint, 11/16"
S 14mm x 1.25mm, .689", taper, 5/8"
V 14mm x 1.25mm, .441", taper, 5/8"
Y 10mm x 1.0mm, .375", gasket/joint, 5/8"
Z 10mm x 1.0mm, .500", gasket/joint, 5/8"
1 to 20 Automotive & small engine
20 to 49 Historical aviation
50 to 65 High performance racing plugs
65 to 100 Industrial & small engine
CENTER ELECTRODE MATERIAL
W Iridium
P Platinum
G Gold palladium
CORE NOSE PROJECTION
RETRACTED No Projection
H .020"-.030"
Y .060"-.090"
M .100"-.140"
L .180"-.220"
E .240"-.300"
2 .020"
3 .030"
4 .040"
5 .050"
Z Skirted plug
LM Lawn mower plug
V Surface gap
B Fine wire rivet design
Use the Champion torque recommendation below as a guide for tightening all spark plugs.
Spark plug wires, also known as ignition cables, are a key part of the ignition system. Car engines that have a distributor or remote coil pack have spark plug wires that transfer the spark from the coil to the spark plug.
Changing spark plug wires on a regular basis is essential to keeping a vehicle’s engine at its best.
Remove and replace one wire at a time, starting with the longest wire. By doing them one at a time, you will not have to worry about accidentally switching the wires. When removing wires from the spark plug or distributor cap, twist or rotate the boot to loosen it from the plug. Do not jerk or tug on the wires or you may break the connection. Be sure to only pull on the boot; do not pull on the cable itself.
When routing spark plug wires to cylinders it’s important to do so in sequence of the firing order to avoid crossfiring. Spacing spark plug wires too close or parallel to each other can also result in crossfiring due to the inductive field which builds up in one wire as the current flows in the other. It’s best to hold spark plug wires in position by using insulated metal, or better yet plastic or fiber brackets to avoid this.
Route the new spark plug wires away from the exhaust manifolds or other metal objects. This protects them from the heat of the manifolds and reduces capacitive voltage loss between the conductor and metal surfaces. Good spark plug terminals are made with a snap ring that give a metallic “click” or “snap” when they are properly set into place. Make sure the terminals are sealed properly and then firmly force any air out of boots and nipples.
Make sure your car?s engine is cold before you start. Underhood environment can be very warm – only remove the spark plugs wires when the engine is cool to the touch. It can take a few hours for an engine to cool.
Wipe off the spark plug insulator and distributor cap towers before installing new wires. Route the plug wires exactly as they were originally. To avoid arc-over, do not route wires of consecutively firing cylinders next to each other.
A couple of things to keep in mind if you have more radio noise upon completion - (1) Metallic wire sets can radiate the ignition noise like an antenna. (2) Always check radio noise with the hood closed and latched. (3) Ensure the spark plug wires aren’t routed parallel to a sensor wire.
Never clamp spark plug wires tightly or allow them to be pinched between the air cleaner and the distributor. The high voltage stresses will be increased at these points and hasten wire failure.
Bundling of spark plug wires and wrapping them with tape, pulling them through metal tubes or dressing them tightly against the engine, may make them look neat but can cause serious voltage losses and/or crossfiring. Changing the routing from the original OEM routing can lead to early spark plug wire failure.
Whether you do a complete tune-up or only change the spark plugs, spark plug wires (also known as ignition cables) should always be checked first. This is necessary due to the aging of the spark plug wires from exposure to extreme temperatures (hot and cold), engine chemicals (oil, grease, coolant, etc.) and electrical stresses. Common signs of failing spark plug wires include a decrease in power, acceleration, and fuel efficiency. In addition, the engine light coming on or visible damange to the cables can be signs of a failing wire.
Be sure to first check spark plug wires for visual damage. Look for any signs of melting or cracking. The following situations call for immediate replacement of spark plug wires:
Tools Needed: Digital multimeter. Use the digital multimeter, set to Ohms ?. Simply attach or hold a meter probe on each end of the cable and read the total resistance on the meter. The Society of Automotive Engineers suggests the maximum resistance should be 12,000 ohms-per-foot. However, some OEMs have recommended different maximum resistances. Consult a tune-up manual for exact specifications.
Tools Needed: 12 Volt light test. Attach the test light to a good engine ground. With the engine running, move the test light along the length of each spark plug wire. If a spark jumps from a plug wire to the test light at any point, this is an indication that the insulation has broken down, and the spark plug wire should be replaced.
Tools Needed: Spark tester. Remove a spark plug wire from any plug. Attach a spark tester to the wire and to an engine ground. Crank the engine and check for a good spark at the spark tester gap.
A good spark will be blue-white and will be plainly visible in daylight. If a good spark is present, the problem is probably not in the ignition system. Check the fuel system and/or stark timing.
Weak sparks are orange or red and may be hard to see in daylight. If you did not see a spark, remove the coil wire from the distributor cap. Attach the spark tester to the distributor end of the coil wire. Crack the engine and check for a good spark at the spark tester. If a spark is present, the problem is probably in the distributor cap, rotor or spark plug wires.
Over time, the spark plugs in a healthy engine develop a slight brown or tan tint of color on the center and ground electrodes. The electrode wear is uniform and like the threads, should appear free of oil and unburned carbon. Here?s a guide on how to detect issues by the color of deposits found on your spark plug.
What to Look For: brown or grayish-tan deposits on the side of the electrode.
What This Means: everything is fine with the spark plug and it should continue to deliver dependable performance.
Note: It is common if you add "off-the-shelf" fuel additives i.e. fuel injector cleaners into your vehicle, this can leave brightly colored residue on the plug.
Even though the deposits you are seeing suggest the plugs are operating normally, it is recommended that you verify the plug gap is set correctly prior to reinstalling the spark plugs.
What to Look For: light brown deposits encrusted on the center and/or ground electrode. These deposits are caused by excessive oil, or fuel additives.
What This Means: if the deposits are on one side of the plug, this is an indication of upper engine wear (valves, seals, cylinder head). If the deposits appear oil around the electrode, this usually means lower engine wear (cylinder, pistons).
What to Look For: oil fouling occurs when oil is allowed to enter the combustion chamber.
What This Means: oil deposits cover the spark plug which can keep the spark from arcing across the gap. Instead it takes the shorter path to ground through the oil. Usually a sign of advanced engine wear.
What to Look For: soft, black, sooty dry deposits on plug indicate carbon fouling.
What This Means: carbon fouling is an indication of a rich air-fuel mixture, weak ignition, or improper heat range (too cold). Carbon deposits are conductive and can create a path for spark plug misfire.
What to Look For: Chalky white insulator (with no tan coloring) pitted or blistered electrodes indicate the plug is running too hot. In some cases the insulator will begin to turn gray or dark blue.
What This Means: Improper heat range plug, lean air fuel mixture, or ignition timing may cause this condition. Pay attention to exhaust restrictions or engine overheating which may also cause plug overheating.
Finding the perfect spark plug wires to fit your car may not always be easy. The good news is that you can always cut and crimp your wires to the length you need.
It’s important to do this carefully. If done incorrectly it may cause a space to occur between the spark plug wire conductor and its terminal. This space reduces continuity, or the flow of electricity in the circuit. Thus a higher voltage build-up in the ignition coil is needed to not only jump the spark plug gap, but also the space left by the faulty termination. This situation tends to produce misfiring of the plug and thus causes difficult engine sharing, poor acceleration and plug fouling.
An improperly terminated lead will result in a reduction in gas milage, increase in emissions and even destruction of a catalytic convert.
Tools Needed: Crimping tool
Lubricate the cable with hand soap or silicone spray and slide the proper nipples and boots over the cable. Wipe off excess lubricant.
Using a crimping tool, strip the ends of the cable 5/8". Always be extremely careful not to nick the IRS conductor, causing the individual fibers to be exposed or fan out like a brush. The coating that binds the conductive fibers together must be intact
Fold the conductor over the cable and insert into the terminal crimp area with the conductor touching the terminal. Keep stripped conductor out of area where crimp ears mee when crimped.
Place the cable and terminal in proper crimping position of tool and crimp firmly. This method of termination will result in a reliable trouble-free connection.
Let?s say you are working on a simple tune-up and during spark plug removal, one breaks off below the hex, leaving the threaded "shell" stuck fast in the head. That can happen with any spark plug but most frequently with the smaller 5/8" hex size. It may never happen to you, but if it does, don?t panic. You?re probably asking what caused it and how do you get the broken piece removed without pulling the head.
The construction of a spark plug shell is like a "hollow bolt". If you exceed the recommended torque, the shell can shear off below the hex. If excessive force is required to remove the plug, it could be traced to one or more of the following causes:
Someone installed the plug with excessive force
Someone cross-threaded the plug during installation
Someone installed the plug in dirty threads
The plug was left installed for too long a time
Unless you installed them, the twist-off is not your fault. However, you?re the one stuck with the job of removing it and you don?t want to take all day. Assuming adequate clearance, in most cases, plug removal can be accomplished with an "easy-out" and a little patience.
You must have the proper tools. We do not recommend a “spiral-cut” type of easy-out; rather we recommend a “square-cut” type design. A spiral cut design has a greater potential of causing the shell to expand, locking even tighter to the cylinder head as removal pressure is applied.
To remove the plug, move the piston to Bottom Dead Center, and make sure the engine is cold, even if you have to wait for cool-down. Then soak the broken plug shell with a generous amount of penetrating oil. Give it a few minutes to work, then tap an appropriately sized easy out firmly into the empty shell. Using an appropriate size socket bar, brace yourself, and while holding the socket squarely on the easy out, apply a firm, steady counterclockwise pressure.
Although the required installation torque on taper seat spark plugs is only 7 to 15 foot pound, we have heard reports of successfully removed spark plugs, without head damage, at torque values exceeding 180 foot pounds!
If you’ve ever tried to remove the original equipment spark plugs from a Ford 4.6L, 5.4L or 6.8L three-valve engine, you might have been reminded of the battery-operated game “Operation” by Milton Bradley. As you might recall, the game’s objective is to extract a body part with absolute precision – otherwise an alarm will sound and the patient’s health will, um, take a turn for the worse.
When replacing spark plugs, ensuring that the plugs have the proper gap is critical to engine performance. The gap is the distance between the center and side electrodes, set so arcing occurs at the proper voltage that ignites the fuel and generates the combustion that makes the engine run.
Not always. In the past, it was necessary to gap spark plugs, but today spark plugs are usually pre-gapped. It is advisable to double check that the gap is correctly set to the vehicle's recommended setting when installing spark plugs.
The gap setting is different for each vehicle but most are somewhere between 0.028" and .060". Consult the owner's manual or Champion® catalog to find the recommended setting for the vehicle you're working on.
Use your spark plug gap tool to adjust the gap. Gently bend the ground electrode in to narrow the gap or bend it out to widen it.
Be very careful when making adjustments. Don't bend the electrode more than a few fractions of an inch. It is durable but isn't designed to take a lot of pressure. Also, take care not to hit the center electrode. If you snap off the bottom electrode or damage the center electrode from excessively prying on it, you'll need a new spark plug. Precious metal iridium or platinum center electrodes can be very delicate when it comes to prying them. It is important to use the proper spark plug gapping tool.
If the spark plug gap is incorrectly set, it can lead to engine issues. The customer may experience loss of power, misfires, spark plug fouling, increased plug wear, or poor gas mileage. Too small of a gap may give too weak of a spark to complete the combustion process within the engine; too wide of a gap can lead to the spark plug not firing correctly, causing misfires at high speeds.