How to Test Ignition Coil with Test Light

In this expert guide, we’ll delve into three distinct methods, each tailored to specific ignition system designs. From the Coil-On-Plug (COP) systems to ignition module type coils and general three-pin designs like the Nissan C.O.P, we’ll unravel the steps and nuances involved in ensuring your vehicle’s ignition system operates at peak performance. Whether you’re troubleshooting a potential issue or simply seeking a deeper understanding, these methods offer a comprehensive approach to testing ignition coils with precision and confidence. So, let’s embark on this journey of automotive expertise and unravel the secrets of ignition coil diagnostics!

The ignition coil is a critical component of a vehicle’s ignition system, and several common issues can arise, affecting its performance. Here are some of the most common problems associated with ignition coils and their potential causes:

Most common causes of ignition coil failure and their signs:

Coil Failure:

Cause: Ignition coils can fail over time due to normal wear and tear. Factors such as heat, vibration, and age contribute to coil deterioration.
Symptoms: Engine misfires, rough idling, poor fuel efficiency, and difficulty starting the vehicle.

Cracked Insulation:

Cause: Exposure to extreme temperatures or physical damage can lead to cracks or breaks in the insulation around the coil windings.
Symptoms: Electrical arcing, coil malfunction, and potential short circuits.

Overheating:

Cause: Continuous exposure to high temperatures, especially in the engine compartment, can cause ignition coils to overheat.
Symptoms: Coil failure, engine misfires, and a decrease in overall engine performance.

Corrosion:

Cause: Corrosion on the coil terminals or connections can occur due to exposure to moisture or environmental conditions.
Symptoms: Poor electrical contact, disrupted signal transmission, and decreased coil efficiency.

Oil Contamination:

Cause: Leaking valve cover gaskets or spark plug tube seals can allow oil to enter the spark plug wells, contaminating the ignition coils.
Symptoms: Electrical shorts, misfires, and potential coil failure.

Incorrect Voltage:

Cause: Issues with the vehicle’s electrical system, such as a malfunctioning ignition control module or power supply problems, can result in incorrect voltage reaching the coils.
Symptoms: Engine misfires, poor performance, and potential coil damage.

Spark Plug Issues:

Cause: Worn, fouled, or improperly gapped spark plugs can put additional stress on the ignition coils.
Symptoms: Reduced engine efficiency, misfires, and potential coil failure.

Carbon Tracking:

Cause: Conductive carbon deposits forming on the surface of the ignition coil can create unintended paths for electrical current.
Symptoms: Reduced electrical efficiency, misfires, and potential coil malfunction.

Environmental Factors:

Cause: Exposure to extreme environmental conditions, such as extreme heat or cold, can contribute to the degradation of ignition coils.
Symptoms: Coil deterioration, decreased performance, and potential failure.

How to test the ignition coil with test light?

The test light proves to be an invaluable tool in the process of testing ignition coils, acting as a guiding beacon for automotive diagnostics. It’s like a detective’s flashlight in the intricate world under your vehicle’s hood. Whether you’re examining a Coil-On-Plug (COP) system, an ignition module type coil, or a three-pin design like the Nissan C.O.P, the test light illuminates the path to understanding your ignition system’s health. From checking for sparks during the Spark Test to observing changes in brightness during Coil Positive and Coil Negative Control tests, the test light provides visual cues, making potential issues more apparent. It’s like a visual storyteller, conveying the condition of your ignition coil with flickers and steadiness. In simpler terms, the test light is your diagnostic companion, shedding light on the mysteries of your vehicle’s ignition system, ensuring you navigate with confidence and precision.

Here we’ll discuss three different methods to test ignition using power probe.

Method 1:

Testing the ignition coil on a Coil-On-Plug (COP) system is a crucial diagnostic step to ensure the proper functioning of the vehicle’s ignition system. Follow these instructions to conduct a thorough ignition coil test:

Equipment Needed:

  • Incandescent test light
  • Test leads with T-pin
  • Multimeter (optional)
  • Replacement ignition coil (for comparison)

Step 1: Spark Test:

Use an incandescent test light with an air gap to ground. Crank the engine to observe if there’s any spark. A lack of spark indicates a potential issue.

Step 2: Coil Positive Test:

With the engine cranking, touch the test light to the coil positive terminal. Observe changes in the test light brightness. Dimming may indicate an issue.

Step 3: Coil Negative Control Test:

While cranking, back probe the coil negative control wire. Ensure a bright and steady test light. Flickering may suggest a problem.

Step 4: Resistance Check on Old Coil:

Measure the resistance on the primary side of the old coil (between two Pink wires). For the secondary side, measure resistance between the tower and either primary terminal.

Step 5: Secondary Measurement on New Coil:

Repeat the resistance measurement on the primary and secondary sides of a new or known good coil for comparison.

Step 6: Test Light Air Gap Verification:

For a functional coil, connect the test light to the coil while cranking to provide a spark path. Observe the waveform on the scope, confirming a proper ramp pattern.

Step 7: Comparison with Bad Coil:

Reconnect the test light to the old (bad) coil. Observe the waveform on the scope, noting any differences from the good coil.

Step 8: Secondary Resistance Verification:

Measure the resistance on the secondary side of the old (bad) coil. Compare the readings with the known good coil and note any significant differences.

Method 2

The method discussed is suitable for vehicles equipped with ignition module type coils. It provides a comprehensive approach to assess the ignition coil’s performance, aiding in the diagnosis and resolution of potential issues. It is recommended for use on various vehicles with ignition module type coils, requiring understanding of circuitry, voltage requirements, and coil specifications for effective application.

Step 1: Vehicle Preparation

Identify the vehicle model and understand its ignition system architecture as different vehicles have differently designed components.

Step 2: Tools Required:

  • Test spark plug (rated at 25,000 volts).Test light.
  • T-pin for back probing.

Step 3: Coil Integrity Check

Locate the ignition coil and its four wires: B+ (power), ground, feedback circuit, and trigger.
Back probe the trigger circuit using a T-pin. Back probing, also known as back pinning, is a method for piercing wire without cutting or stripping the insulation. It’s used when live circuit measurements are needed.

Remove the coil and connect the test spark plug to a good ground.
With the ignition turned on, use the test light (connected to B+) to simulate the computer trigger.
A properly functioning coil should generate a bright blue spark, easily jumping the 25,000-volt gap in the test plug.

Step 4: Interpretation

A strong spark indicates the coil’s integrity and its ability to fire across the specified gap.
If the spark is weak or absent, it suggests a potential issue with the ignition coil.

Step 5: Repeat for Different Systems

Repeat the process for other vehicles with ignition module type coils.
Identify the power, ground, and trigger wires, and adapt the test according to the specific voltage requirements of the vehicle’s system.

Step 6: Quick Tip

Understand the circuitry, voltage requirements, and coil specifications for different vehicles.
Use this method as a quick diagnostic tip when working on vehicles with ignition module type coils.

This comprehensive method allows you to efficiently assess the ignition coil’s performance, aiding in the diagnosis and resolution of potential issues.

Method 3:

In this guide, we’ll walk you through the process of testing an ignition coil using a test light. This method is particularly relevant for coils with a three-pin design, such as the C.O.P design. Testing involves assessing voltage and current levels to ensure the coil is functioning correctly. This test can be valuable, especially when diagnosing a single-cylinder misfire. It helps differentiate between a faulty coil and potential wiring or computer issues.

Connect the test light in series with the multimeter.
Touch the test light on the battery positive to establish a baseline reading.

Step 1: Baseline Readings:

Note the initial surge and constant current flow through the test light. Pay attention to any spikes, especially on initial turn-on, and consider the impact of temperature on these readings.

Step 2: Coil Inspection:

Examine the coil you’re testing. If possible, inspect the coil’s design and understand its internal components.

Step 3: Base Circuit Measurement:

Before proceeding with the bypass test, measure the voltage of the base circuit by cranking the engine over. Connect the Vantage Pro to measure both voltage and current on the base circuit.

Step 4: Bypass Test:

Conduct the bypass test by triggering the coil with the test light. Be cautious not to overheat a good coil by keeping the dwell time momentary.
Use an incandescent and an LED test light separately for comparison.

Step 4: LED vs. Incandescent Test:

Connect the test lights to the base circuit wire and observe the amperage and voltage readings on the Vantage Pro or multimeter. Note the differences between the incandescent and LED test lights in terms of surges, voltage, and current draw.

Step 5: Evaluate Results:

Evaluate the results of the bypass test. A successful spark when there was none before indicates a functional coil. If no spark is observed, there may be issues with wiring or the computer.

Step 6: Test Light Choice:

Consider using an LED test light for this procedure, as it generally keeps the current draw on the base circuit to a minimum.

Caution:

Be aware that voltage and current levels observed during the test are influenced by the specific test light used and the internal resistance of the coil. Results may vary for different coil designs.

Conclusion

There are different methods for different types of ignition systems, such as Coil-On-Plug (COP) and ignition module type coils. These methods help you make sure your ignition system is working well. Whether you’re fixing a problem or just learning more, these methods act like helpful guides for testing your ignition coil. Think of the test light as a tool that helps you spot issues during tests like Spark Test, Coil Positive, and Coil Negative Control. It’s like a storyteller, showing you how your ignition coil is doing with its brightness. The test light is a helpful tool, making it easier for you to understand and fix any problems with your car’s ignition system.

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