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Coil Pack – Symptoms Of A Faulty Ignition Coil And How To Test Them

coil pack

The coil pack within your car is an important piece of the ignition system. Without the coil pack properly functioning, the ignition system won’t work, and your car won’t start. Although numerous parts of your car are imperative and must work together in order to function at an optimal level, the coil pack may be one of the most important components in starting your car and engine. Replacing a coil pack consists of fixing the ignition coil. The average price of fixing the ignition coil is between $264-$376.

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What Is A Coil Pack?


A coil pack is an electronic piece of equipment within the ignition system. This electronically-controlled pack consists of ignition coils that are controlled by the car’s main computer. The main job of the coil pack is to increase and build the energy needed, and then release the voltage through the spark plug cables. When the energy reaches the spark plugs, it starts the combustion process. 


In more modern cars today, the distributor is replaced by the coil pack. This is typically because the coil pack is more reliable and consistent than the distributor. In addition, the coil pack provides a better spark, which causes more efficient and quicker combustion, along with higher horsepower. 


What Is An Ignition Coil?


As we said, the ignition coils make up the bigger coil pack. An ignition coil is an induction coil in a car’s ignition system. An induction coil is a spark coil that produces a high voltage from a low voltage supply. The job of the ignition coil is to transform the battery’s lower voltage to a much higher voltage that is needed to create the electric spark in the spark plugs. The spark created will then, in turn, ignite the fuel. 


The electric spark generated due to the high voltage is a quick electric discharge that occurs as a result of an ionized and electrically-conductive channel. The electric spark occurs in the spark plugs. The spark plugs are devices for delivering the electrical current from the ignition system to the combustion chamber of the engine. They will then be able to light the compressed fuel and air mixture by the electrical spark created, while simultaneously keeping the correct level of combustion pressure in the engine. A common cause of the ignition coil failing is due to a spark plug gap. 


Energy Process Of Ignition Coil


The ignition coil consists of an iron core surrounded by two coils of copper wire. The ignition coil contains a magnetic circuit, meaning the iron core doesn’t form a closed loop. The energy kept in the magnetic field of the core is the energy transferred to the plug. 


Within cars, smaller coils are used with one coil for each spark plug. A larger ignition coil can produce about 40 kV. These coils can be mounted on top of the spark plug, and are called a direct ignition plug. Coils can also serve two spark plugs, and are called the wasted spark system.


The wasted spark system consists of one coil generating two sparks per cycle to each cylinder. The fuel within the cylinder can then be ignited. The wasted spark system is more reliable than a single-coil system, and is also less expensive than a coil-on-plug option. 


How To Tell If An Ignition Coil Is Bad – Symptoms Of A Bad Coil Pack


If you’re having an issue with the coils, you can usually tell by a few signs and symptoms that there’s something wrong. There are a few key steps you should take to determine if the problem is going on with your ignition coil, coil pack, or another part of your car.


First, you should test the coils with a multimeter. Ignition coils retrieve energy from the battery, which is usually at least 12 volts. The coils then convert the energy to a higher voltage, of atleast 50,000 volts, in order to create a spark. This energy then travels via the distributor to the spark plugs, and then ignites the fuel. Some vehicles only have a couple of ignition coils that can power various spark plugs – remember the wasted spark system we were discussing earlier. Other models use one ignition coil per plug. 


The number of coils is irrelevant to this next step – you need to remove all of your coils, no matter the amount you have. Before you start, make sure you have a multimeter and tool kit. Here are the symptoms you need to look for as the signs of a bad ignition coil.




If your vehicle backfires, then you will almost certainly notice. The loud noise and shaking sound will clue you in that there is something wrong with your car. A strong blast, your car lurching forward, and black smoke coming out – it’s kind of hard not to notice. The check engine light may also come on, and you might smell gasoline coming out of your car. 


Sometimes low fuel pressure could be the culprit. However, most of the time this issue is due to the ignition system. Faulty ignition coils can affect the timing of when the spark plugs ignite, which causes misfiring and bad timing. Backfiring of the engine is a symptom of a bad coil pack. 


Engine Stalling


A vehicle that is stalling will undergo abrupt stops and starts, making it incredibly difficult and frustrating to drive – and not to mention quite dangerous. If one or more of your ignition coils under the hood begins to fail, this can cause the car to stall. The coils will send irregular sparks to the spark plugs. The electrical charge provided will be uneven and prevent the engine from running at a consistent and smooth rate. The engine stalling is a symptom of a faulty or bad coil pack.  


Lower Fuel Economy


If your ignition coil does not transmit enough energy to the spark plugs in your car, your vehicle will have to burn and use extra fuel. This is the only way that the vehicle can keep running – by burning the extra and residual fuel. If your car is getting very poor gas mileage and a lot lower than normal, then you might have a faulty ignition coil.


Be sure to know the amount of miles per gallon your car can usually drive, and then take your car for a short test drive. If you are unsure of the typical miles per gallon, check your dashboard for the odometer and calculate the miles you have driven, and the average miles per gallon you typically receive.


Difficulty Starting The Engine


If you have trouble starting the engine, you might automatically assume the battery is the issue. Sometimes, however, the ignition coils are the real culprit. They can cause serious problems if your vehicle has a one-per-plug system instead of a wasted spark system. The car can run if a few ignition coils are damaged or are faulty, but it won’t be able to start as easily or smoothly. 


Occasional Idling


If you experience your car idling unexpectedly, then you could have a faulty coil pack or ignition coils to blame. In addition, your car will have less power while running, a sure sign that something is wrong with your ignition system.


If you find that your vehicle is experiencing one, or multiple of these problems, then it is time to test your ignition coils. Find the multimeter and your toolbox and follow these simple steps to test your ignition coils. 


How To Test Your Ignition Coils



  • Set Up The Car For Work



Before you start any internal work in your vehicle, you need to make sure that your vehicle has cooled down from any driving or idling. After it is cooled off, switch the emergency brake on. Open the hood and disconnect the negative battery cable attached to the battery end terminal. If needed, you might require a tool like a wrench to disconnect the cable. 



  • Remove the Ignition Coils



First, you need to locate the ignition coils. Look near or on the engine for the coil pack. Disconnect the mounting bolts that are stabilizing the ignition coils, and then remove each coil from the engine area. 



  • Test the Primary Winding



Each ignition coil will consist of two separate coils wrapped around each other – this is called the primary and secondary winding. The primary winding is usually made of heavy wire. This wire receives energy from the battery directly. Be sure to test this heavy wire portion of the coil first. 


Connect the multimeter positive and negative leads to the correct terminals on the ignition coil, being sure to read which lead goes on which end. Each terminal will be marked with symbols that correspond to the positive and negative leads, such as a plus and minus sign. Be sure to check the owner’s manual to see what the end symbols look like before plugging in the leads.


Note the reading on the multimeter and compare this number to the resistance needed for the primary winding. See if the reading is normal for the specifications, or if it has a faulty reading. If the reading is outside of the normal range, you will need to replace the resistance coil. If the reading comes up as zero, then your coil might have shorted-out internally. If the reading of your coil is extremely high, it means the coil is open. An open reading means the coil is still in working condition – if this is the case, you can move onto the next step.



  • Test The Secondary Winding



The secondary winding is a wire that is thinner than the primary winding, and wraps around the coil numerous times. It gains energy from the primary winding, and then transmits the energy to the spark plugs. The process for testing the secondary winding is similar to testing the primary winding. 


First, you need to connect the correct multimeter leads to the positive terminal and the center pole. The center pole is the area in which the main wire attaches to the distributor. Take note of the multimeter’s reading and compare it to what the reading should be for the proper specifications regarding the secondary winding. If the reading is outside of the correct range for optimal performance, you need to replace the ignition coil.



  • Solve The Issue



If your vehicle has multiple ignition coils, then you will need to remove and test each ignition coil separately. Take note of the readings via the multimeter, and then reinstall or replace each one depending on the reading information. 


Check The Spark Plugs Too


While you are testing the alternator, you should also check the condition of the spark plugs. The ignition coils can fail due to faulty spark plugs – it is actually the most common problem and cause of ignition coil failure. Bad spark plugs can overload the ignition coils and overwork them. If you don’t solve the spark plug issue, the oils will fail again. 


How Much Does It Cost To Fix The Ignition Coil?


The average cost to fix the ignition coil is around $264-$376. This average price includes the labor work and the cost of the parts. The labor costs are around $99-$126 for them to perform the service. The parts are an average of $165-$250. 


What If I Don’t Want To Test And Fix My Ignition Coils Or Coil Pack?


If you don’t want to go through the effort of testing, diagnosing, and paying to fix your ignition coils and coil pack, you can sell your car to a junk car company for some extra money. Remove all non-metal components, and sell them for additional cash. If you tested your ignition coil and it is working correctly but you still want to sell your car, you can sell your ignition coil for some cash – this is one of the most sought-after parts today. After you have sold the necessary parts, bring your car to CashCarsBuyer for a fair quote – and some quick money!


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