How to Test Your Car's Ignition Coil: A DIY Guide

by:Haiyan     2023-11-02

How to Test Your Car's Ignition Coil: A DIY Guide


The ignition coil is a crucial component in your car's ignition system that is responsible for producing and transferring high voltage energy to the spark plugs. Over time, the ignition coil can wear out, leading to engine misfires, poor fuel efficiency, and even difficulty starting the vehicle. Testing the ignition coil regularly is essential to ensure optimal performance and prevent potential issues. In this DIY guide, we will walk you through the step-by-step process of testing your car's ignition coil to diagnose any problems and take appropriate action.

1. Understanding the Ignition Coil:

Before diving into the testing process, it is essential to understand how the ignition coil works. The ignition system includes an ignition coil, distributor, spark plugs, and various wiring connections. The coil consists of two windings - primary and secondary. The primary winding receives low voltage from the car's battery, while the secondary winding produces high voltage required to create sparks in the spark plugs.

2. Symptoms of a Faulty Ignition Coil:

Identifying the signs of a faulty ignition coil is crucial to determine if a test is necessary. Here are some common symptoms:

a. Engine Misfires: If you notice sudden jerking or misfiring of the engine, it could indicate a problem with the ignition coil.

b. Decreased Fuel Efficiency: A faulty ignition coil can lead to inefficient combustion, resulting in reduced fuel efficiency and increased emissions.

c. Difficulty Starting the Vehicle: When the ignition coil fails, starting the vehicle might become a challenge. If you experience prolonged cranking or inability to start, it may be due to a faulty coil.

d. Engine Stalls: A failing ignition coil can cause the engine to suddenly stall, leading to potential safety hazards.

3. Preparation for Testing:

Before testing the ignition coil, gather the following tools: a digital multimeter, a 12-volt test light, and the vehicle's service manual for reference. Ensure that the engine is turned off and has completely cooled down before beginning the testing process.

4. Testing the Primary Winding:

The primary winding is responsible for receiving low voltage from the battery. To test this winding:

a. Locate the ignition coil in your vehicle. It is usually situated near the engine and has thick wires connected to it.

b. Disconnect the wires connected to the ignition coil. Carefully remove them to access the primary winding terminals.

c. Set the multimeter to the ohms setting. Touch the meter leads to the positive and negative terminals of the primary winding and note the resistance reading. Refer to your vehicle's service manual to determine the acceptable range. If the resistance falls outside the specified range, the primary winding might be faulty.

5. Testing the Secondary Winding:

The secondary winding generates high voltage required for spark plug ignition. Follow these steps to test the secondary winding:

a. Reconnect the wires to the ignition coil's primary terminals.

b. Locate the spark plug wires connected to the ignition coil. Disconnect them carefully.

c. Connect one end of the 12-volt test light to the positive terminal of the coil and the other end to a good ground on the engine.

d. Have someone crank the engine while you observe the 12-volt test light. If the light flashes, it indicates that the secondary winding is functioning correctly. If not, the secondary winding may be faulty.

6. Checking for External Issues:

Sometimes, the faulty ignition coil symptoms can be caused by external factors. Perform these checks before concluding the coil is faulty:

a. Inspect the ignition coil for cracks, corrosion, or any physical damage. If such issues are present, replace the coil.

b. Check all the wiring connections associated with the ignition coil for loose or damaged connections. Tighten or repair any problematic connections.

7. Consult a Professional:

If you have followed the testing procedures outlined in this guide and suspect a faulty ignition coil, but are still unsure, it is recommended to seek professional help. A certified mechanic will have specialized tools and expertise to diagnose the issue accurately and provide suitable solutions.


Testing your car's ignition coil is a simple yet crucial task to ensure your vehicle's optimal performance. By following this DIY guide, you can identify potential issues and take appropriate measures to prevent further damages. Remember to exercise caution, refer to your vehicle's service manual, and seek professional help when needed. Regular maintenance and testing of the ignition coil will keep your car running smoothly and efficiently.

Custom message
Chat Online 编辑模式下无法使用
Leave Your Message inputting...