A coil pack, simply put, is an electronically controlled pack of ignition coils controlled by the car’s computer.

Its main responsibility is to build up the energy and then release the voltage through the spark plug cables so it can reach the spark plugs–and that’s how the combustion process starts.

In modern cars, the distributor is replaced by this device because of two reasons: 

1. It is more reliable and
2. It provides a better spark, which results in more efficient combustion and higher horsepower.

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HOW IGNITION DISTRIBUTOR WORKS?

Download: REPAIR GUIDE FOR DENSO COMMON RAIL INJECTOR REPAIR

OVERHAULING A BOSCH DISTRIBUTOR

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What will happen if you have a bad coil pack?

Once the coil pack fails, engine misfiring can happen because one or more spark plugs in the engine cylinders didn’t receive enough voltage. 

This will usually cause a drag on the crankshaft; hence, a poor performance from your engine.

FIRING ORDER: ITS PURPOSE AND ORDER IN DIFFERENT NUMBERS OF CYLINDERS

DIFFERENCE BETWEEN CRANKSHAFT AND CAMSHAFT

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Read More:

• INSPECTING THE IGNITION SYSTEM
• HOMOGENEOUS CHARGE COMPRESSION IGNITION (HCCI) ENGINE
• DISTRIBUTORLESS IGNITION SYSTEM (DIS) – MAIN COMPONENTS, WORKING WITH APPLICATION
• HOW IGNITION DISTRIBUTOR WORKS?
• CAPACITOR-DISCHARGE IGNITION(CDI) WORKING PRINCIPLE, ITS ADVANTAGE AND DISADVANTAGE
• HOW TO FIX IGNITION IF WHEN YOUR VEHICLE HALTS IN THE WET WEATHER?

QUIZ: ARE YOU AN IGNITION EXPERT? TAKE THE QUIZ!

What are the common symptoms of a faulty coil pack?

A faulty coil pack has pretty similar symptoms to a failing spark plug including rough idle, unusually louder engine, a noticeable drop in RPMs when accelerating, and significant lack of power.

You might also notice your check engine light blinking or the gas warning light activating even when the gas tank is full.

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Read: SPARK PLUGS AND GLOW PLUGS: WHAT’S THE DIFFERENCE?

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How to make sure that the coil pack isn’t the problem in your vehicle?

Fortunately, there’s a fairly easy test that you can perform to make sure that the coil pack is working properly.

What you need to do is to use an ohmmeter to check each coil’s primary and secondary resistance.

For the primary resistance, the ohmmeter should be set to the 10 ohms range.

Also, Read: CHECKING THE HIGH-TENSION CIRCUIT

Then you need to touch one of the meters leads to the centre prong on the electrical connector of the coil pack.

If the reading is between 0.3 and 1.0 ohms, then it’s good. It’s the same thing for the second resistance.

This time, however, the ohmmeter should be set to 20,000 ohms.

The reading should be between 5,000 and 10,000 ohms.

This process should be done on each coil.

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