In simpler words, a coil pack is a bundle of ignition coils controlled by the vehicle’s computer (ECU) that electronically manages spark timing for each cylinder.
The coil pack integrated within your vehicle is an essential component of the ignition system. If the coil pack does not work properly, the ignition system becomes inoperative, which means that the vehicle cannot be started.
Although many essential parts of the vehicle system are designed to work in unison for optimal efficiency, the vehicle coil pack is arguably the most critical component when it comes to starting an engine.
When the coil pack is damaged, an individual coil may not receive adequate voltage, leading to misfires due to some spark plugs not firing in their respective engine cylinders. Coil pack replacement is specified as repairing the ignition coil. The average cost to fix an ignition coil is anywhere between $264 and $376.
What Is A Coil Pack?
A coil pack is part of an electric module of the ignition system. It consists of multiple combustion coils controlled by the car’s central computer system (ECU).
To summarize, a coil pack is responsible for creating and storing requisite energy, then discharging voltage through the spark plug cables. The energy provided to the spark plugs initiates combustion.
The coil pack superseded the distributor in modern cars. This is mostly because the coil pack is more dependable and uniform than a distributor. Furthermore, greater combustion efficiency along with increased horsepower is provided by the enhanced spark from the coil pack.
Coil Packs: A Quick History
In the mid-1980s, coil packs capable of firing two “companion” cylinders at once made their appearance as replacements for distributors. Companion cylinders are those in four-stroke engines where two companion pistons achieve top dead center simultaneously.
In other words, coil packs are fired at the precise moment each piston reaches the top of the stroke. However, energy is spent only by the firing cylinder. Waste spark is hence the term used for this type of ignition, since spark plugs fire even during the exhaust stroke.
Motorcycles have used this type of ignition for literally decades, but there are still primary and secondary windings in the coil pack that are energized when the ignition key is turned on. Pulsing ground voltage is supplied from an ignition module or ECM/PCM to complete the circuit.
What Is An Ignition Coil?
To pull it all together, the coil pack is made up of a number of ignition coils. An ignition coil is classified under induction coils, which are a part of the car’s ignition system. An induction coil is also referred to as a spark coil, since its function is to convert low voltage into high voltage.
Ignition coils are responsible for transforming lower voltages from the battery into significantly higher voltages for the electric spark needed in the spark plugs. This electric spark subsequently ignites the fuel.
Due to the high voltage, there is a rapid electric discharge, which is the outcome of an ionized and electrically conductive channel. The discharge of electricity, termed a spark, forms in the spark plugs.
The combustion chamber of the engine is reached by an electric current facilitated through an ignition system by devices called spark plugs.
With the pressure within the engine appropriately regulated during combustion, the fuel and air mixture gets ignited with an electrical spark. One of the more common reasons for an ignition coil to fail is due to a gap in the spark plug.
Energy Process Of Ignition Coil
The copper wire that forms the two coils of the ignition coil is wound around an iron core. An ignition coil has a magnetic circuit. This means that the iron core does not have a closed loop. The energy stored in the magnetic field of a coil is set free when the coil is declutched. In this case, it is given to the plug.
Inside cars, the smaller coils are used with one coil for each spark plug. A larger ignition coil can produce around 40 kV. These coils are also called direct ignition plugs and can be mounted on top of the spark plug. Coils can also serve two spark plugs and are called the wasted spark system.
The wasted spark system comprises one coil that generates two sparks for each cycle to every cylinder. The fuel in the cylinder is then ignited. This system is more reliable than a single-coil system and is less expensive than a coil-on-plug system.
Types of Ignition Coils
As per the system in a vehicle, two to three types of ignition coils are commonly used. These types include:
- Traditional ignition coils – These analog coils are fixed to a distributor, and older cars came equipped with them. These coils utilize wires to connect to the spark plugs and are known to have a plethora of symptoms when they fail, such as hard starting, backfiring, rough idling, misfiring, or even decreased fuel efficiency across all cylinders.
- Coil-on-plug (COP) – Evolving from older vehicle models, these springs are commonplace in modern vehicles and are located directly under each spark plug. This means that individual wires from a spark plug to the coil are not needed. With each cylinder having its coil, there are fewer issues per cylinder, which makes it easier in terms of diagnosis.
- Distributorless ignition system (DIS) – This system has one or a group of coils that ignite more than one plug at a time, doing away with a distributor. However, there are some drawbacks, as in DIS systems, one broken coil impacts several cylinders, although not all of them may be affected at once.
How To Tell If An Ignition Coil Is Bad?
More often than not, there will be symptoms that will very clearly show that there are issues with the coils. Here’s a set of steps that will help you identify if the issue lies with the ignition coil, coil pack, or another component of the vehicle.
To begin with, you should check the coils with a multimeter. Ignition coils pull energy from the battery, usually no lower than 12 volts. Their coils are also capable of creating an even stronger voltage of at least 50,000 volts, so they can produce a spark.
This energy is then sent to the distributor, from where it travels to the spark plugs, where the fuel is ignited. Subsequently, only a few ignition coils can provide a few spark plugs – do you remember the wasted spark system we were talking about earlier? Other types use one ignition coil for each plug.
Skip this step. It has no relation to the number of coils you have. You need to take out all of your coils. Additionally, ensure that you have at hand a multimeter and a tool kit, as they will be needed.
8 Signs of a Faulty Ignition Coil
Let’s start by telling you what signs indicate your ignition coil might be failing.
Your Car Guzzles Gas
Having to refill at the gas station frequently, without increased mileage on the odometer, could be due to issues with the ignition coil. It impacts the flow of power the battery sends to the spark plugs, which results in the car consuming more fuel.
Your Car Feels Slow
Feeling sluggish while responding to the accelerator could be the result of a faulty ignition coil. Your car’s air-fuel mixture is most likely not being ignited properly, leading to your vehicle feeling less responsive.
You Hear Spluttering, Coughing, and Banging Noises
Your car issues sputtering and coughing sounds are caused by a failing ignition coil. The noises originate from a cylinder that is either not firing or not completing the firing sequence during the ignition cycle. The loud banging is gas that combusts and explodes inside the combustion cylinders and is never utilized.
Your Car Idles Roughly and Vibrates
Your vehicle’s shaking and vibrating while idling could suggest issues with the coil. Rough idling and car vibration are indications of an ignition coil problem. A faulty coil will lead to many issues, including an incomplete spark being sent, resulting in jerking when trying to accelerate.
Your Car Misfires and Backfires
An ignition coil problem can prevent one of the cycles of four-stroke engine from firing and result in backfiring. Backfiring indicates that a cylinder is failing to fire or partially fires. An incomplete fire on certain cylinders can lead to a breached catalytic converter, among other parts of the engine. There may be gas fumes alongside smoke emitted from the tailpipe.
Your Car Stalls
A staggering coil will make starting the car difficult. When coming to a stop, the vehicle may stall unexpectedly.
You Struggle to Start Your Car
While more contemporary vehicles utilize a coil to fire every cylinder, older makes used one coil. If a car’s ignition coil is damaged, it won’t supply proper voltage to the spark plugs. Your car will attempt to crank over, but will not engage.
The Check Engine Light Is On
Hard starting, backfiring, and misfiring will light up a vehicle’s check engine light. It is critical to never overlook the engine light on the dashboard. Repairs should be made without undue delay to prevent further damage, which will result in higher repair expenses.
How to check the ignition coil?
In testing an ignition coil, use the following equipment:
- A multimeter with the ability to measure the resistance of the ignition coil.
- A spark tester to guarantee that combustion will occur.
- A general-purpose tool kit, such as a screwdriver and a socket wrench.
- The vehicle’s manual will assist in finding the ignition coils and checking their specifications for adjustments.
For more detailed diagnostics, consider:
- A detailed analysis one the voltage produced by the ignition coil output is, an oscilloscope.
- OBD-II scanner is helpful to detect problems associated with ignition system breakdowns.
Step-by-Step Guide to Testing Your Ignition Coil
Step 1: Perform a Visual Inspection
Critically evaluate the coil housings to determine whether any form of physical damage is present. For instance, look for cracks, burnt portions, scratches or even deformed plastic on the coil housing.
Failure of the coil may also be a result of damaged wiring or connectors. In case you find a damaged part, it is important to note that there are no other options other than replacing the damaged ignition coil.
Step 2: Test Resistance
Using a multimeter allows for verification of the cylinders ‘primary and secondary windings’ resistance.
- First, you need to switch off the engine and then remove the ignition coil from its mount.
- Secondly, set your multimeter to ohms (Ω) and start with the coil’s primary terminals, where you can expect a reading of 0.4 to 2 ohms.
- Depending on the vehicle, at the positive terminal, there also needs to be an output terminal that is connected to the spark plug. It is reasonable for one to expect the output coil resistance to be around 6000 to 10,000 ohms while the coil is in healthy condition.
As indicated earlier, if multimeter readings are lower than expected, that simply means the ignition coil is and needs to be replaced.
Step 3: Check for Spark
If multimeter readings suggest everything is okay but you suspect there is still a problem, use a spark tester to check for a clear, strong spark.
- Reinstall the ignition coil and attach the spark tester to the coil and a grounded region of the engine.
- Turn the engine on or crank it. Look for a strong blue spark in the gap of the spark tester.
- If you do not see a spark or the spark is too weak, the ignition coil is most likely defective and needs to be replaced.
What to Do After Testing Your Ignition Coil
It is advised to replace the ignition coil if the resistance readings or the spark test points to an issue. If all tests are performed and checked, but persistent signs are still there, the problem may be with other components of the ignition coil, control module, or wiring.
There is no defined interval for replacing coils; however, replacing them after every 100,000 miles is reasonable.
It is more common. Unlike other electrical components of a vehicle, ignition coils will age with use. But if neglected parts such as spark plugs are not serviced, coils will fail sooner than expected. Always use high-quality components to increase reliability and lifespan.
Being able to test a spark plug coil can help in diagnosing ignition system problems and enabling a vehicle to perform optimally.
How Much Does It Cost to Replace an Ignition Coil?
The cost for ignition coil replacement largely depends on a vehicle’s make and model, as well as the ignition coil being used. For ordinary cars with standard ignition coils, the average cost for replacing one ignition coil is between $100 and $300.
For COP (coil on plug) or other advanced ignition systems like DIS (distributorless ignition system), the costs tend to be higher, averaging $200 to $600 per coil.
Also, two other factors must be considered when calculating the total cost of replacing ignition coils: the ignition coil’s purchase price and labor. Depending on the type and quality, ignition coils cost around $50 to $200 each.
Labor for replacing ignition coils tends to be calculated on an hourly basis. Average labor costs per hour usually range from $50 to $150, depending on the location and the repair shop.
The time required to replace an ignition coil may range between half an hour to two hours, based on the design of the vehicle and the number of coils needing replacement.
As an example, the total cost of replacing a single ignition coil in an automobile with standard ignition systems may range from $150 to $350, which includes the cost of the coil as well as the labor charges.
However, in Advanced vehicles, with other ignition systems that also require more expensive coils and more time to replace them, the cost could easily escalate to $300 to $800 or more.