10 Bad Ignition Coil Symptoms on an ATV (How to Check)

The ignition coil is vital to your ATV’s engine. It generates the high voltage required to ignite the air-fuel mixture in the combustion chamber. When faulty, it can disrupt this process and result in a slew of performance issues. In this article, let’s explore its symptoms when bad and go through the steps leading to its resolution.

Here are ten symptoms of a bad ignition coil on an ATV:

1. Misfiring
2. Loss of Power
3. Rough Idling
4. Starting Irregularities
5. Activated CEL
6. Reduced Gas Mileage
7. Backfiring
8. Cold-Starting Difficulties
9. Engine Stalling
10. Increased Emissions

Diagnosing the symptoms involves measuring resistance readings, ruling out defective components, and examining the ignition coils and spark plugs.

Through thorough inspection and relevant tests, off-roaders can ensure the integrity of an ATV’s electrical system and its capability to supply power where needed. Moreover, performing these establishes a methodical and comprehensive method for diagnosing your ATV pain points — effectively addressing ATV bad ignition coil symptoms and any other concerns stemming from a quad’s electrical system.

What Does an Ignition Coil Do on an ATV?

The ignition coil is “essentially a wire-based transformer,” according to Haynes (as quoted by Motor Biscuit), and typically consists of two wire coils around an iron core. It holds or houses the magnetic field formed when an ATV’s primary ignition completes a circuit and transmits power from the battery to the ignition coil and then back.

It’s also interrupted by the secondary ignition, which could have a distributor, distributor-less, or coil-on-lug system. This interruption by the secondary ignition makes turning the 12V from the battery into 50,000 volts (or more) and having this high-voltage jumping current power the spark plugs possible.

Although we’re not electrical engineering majors, it’s important for us, off-roading enthusiasts, to understand this crucial process. The reason is that, in most cases, issues with the ignition coil can mask themselves as spark plug problems. It’s understandable since both components are part of the ignition system.

ATV Bad Ignition Coil Symptoms

1. Misfiring

A faulty ignition coil can cause misfiring, where the engine skips or stumbles during acceleration. This results in uneven power delivery and a noticeable decrease in performance.

2. Loss of Power

An ATV with bad ignition coil symptoms may also experience reduced power output, especially when climbing slopes or during acceleration. The lack of a strong spark can lead to incomplete combustion and diminished engine performance.

3. Rough Idling

A damaged ignition coil can disrupt the smooth idle of your ATV’s power mill. You might notice the engine running erratically, with uneven RPMs and occasional shaking or vibration.

4. Starting Irregularities

A faulty ignition coil often results in persistent difficulties starting the ATV and needing more attempts or prolonged cranking before the engine fires up.

5. Activated CEL

Apart from starting issues, a malfunctioning ignition coil can make the Check Engine Light appear on the ATV’s dashboard. Because of the compromised ignition coil’s failure to play its role, the ECU eventually detects irregularities in ignition and combustion — prompting the CEL to illuminate.

6. Reduced Gas Mileage

Defective ignition coils can lead to inefficient combustion, increasing fuel consumption. When this happens, you may find yourself making more frequent visits to the pump station and your ATV covering fewer miles per gallon due to incomplete burning of the air-fuel mixture.

7. Backfiring

In some cases, a malfunctioning ignition coil can cause backfiring through the exhaust or intake. This occurs when unburnt fuel ignites in the exhaust or intake manifold, leading to loud popping noises.

8. Cold-Starting Difficulties

If faulty ignition coils can make firing up the engine in normal weather a tedious task, what more with cold starts! Because the engine requires a stronger-than-normal spark during colder weather, it would make sense to encounter issues in this area when the ignition coil becomes damaged or compromised.

9. Engine Stalling

One of the more dangerous aftermaths of an unreliable ignition coil is causing the engine to stall suddenly during operation — leading to unexpected shutdowns.

10. Increased Emissions

Finally, inadequate spark can result in incomplete combustion and higher emissions of unburnt fuel and pollutants.

While these telltale signs are not exhaustive, they paint a pretty clear picture of how your ATV ownership and riding experience would be if you leave ignition coil issues unattended.

Personally, I wouldn’t want any of these complications to ruin the mood during my weekend adventures. That said, I’ll make it a point to resolve coil-related issues as soon as possible by heeding the advice in the next section.

How to Check an ATV Ignition Coil

In a post by Big Bike Reviews, it was recommended to rule out a compromised motorcycle reg-rec first. For ATVs, however, it’s the other way around. Diagnosing potential ignition coil issues is more of a low-hanging fruit. Generally, it needs to be prioritized over more intricate tests like a diode leak or regulator-rectifier test.

Nonetheless, the decision to do a specific test as a first step ultimately hinges on the situation or symptom a rider or ATV owner is faced with. That said, here are some guidelines to help clarify things a bit:

Test the regulator-rectifier first:

• If experiencing problems related to the ATV’s battery charging system (e.g., dead battery, inconsistent battery voltage, or starting difficulties due to a low or weak battery)
• If various electrical components (e.g., lights, gauges, etc.) are malfunctioning or behaving erratically

Test the ignition coil first:

• If the quad is having trouble starting or is experiencing misfires, poor acceleration, backfiring, or any other performance issues related to spark generation
• If not getting a spark at the plugs or suspect ignition-related issues.

Should your machine’s dilemma and symptoms fall under the first two bullets, then here are the different tests you can do on your ATV depending on the severity of the problem:

• Regulator bypass
• Open-circuit voltage test
• DC voltage regulator test
• Diode leak test
• Voltage drop test
• Regulator-rectifier test

Otherwise, the subsequent steps would be more relevant to your ATV’s ignition coil:

1. Prioritize Safety.

Before fixing any issues with your ATV’s ignition coil:

1. Ensure the quad is parked on a flat and level surface.
2. Double-check that the ignition is turned off.
3. Remember to wear gloves and goggles for your safety to avoid accidents or harm while working on your ATV.

2. Find the Ignition Coil.

Once you’re appropriately clad, and your machine is on even ground, look for the ignition coil on your quad. Depending on the year, make, model, and layout of its ignition system, you may find the ignition coil in one of three places specified below:

Distributor. In an ATV with a distributor mechanism, the ignition coil is often positioned near or on the distributor. It makes perfect sense since the distributor is responsible for distributing the high voltage from the coil to each spark plug in a specific firing order.

Distributor-Less. In ATVs with a distributor-less ignition system (a.k.a. direct ignition system or DIS), individual ignition coils are usually located directly above or adjacent to each spark plug. This setup allows for more precise control over ignition timing and eliminates the need for a central distributor.

Coil-on-Plug. In ATVs utilizing a coil-on-plug mechanism, each spark plug has its own dedicated ignition coil directly mounted on top of it. This efficient design helps minimize energy loss by delivering high-voltage current directly to the spark plug.

3. Examine the Ignition Coil.

Inspect the ignition coil visually for physical damage like cracks or corrosion. Also, gently wiggle the coil and connectors to ensure proper connections. Check the housing, terminals, and wiring for abnormalities, as visible damage could indicate a faulty coil requiring repair or replacement.

Furthermore, confirm the secure mounting of the coil in its designated location. While at it, look for loose or missing bolts or brackets and replace any worn attachments to maintain stable coil positioning during operation.

Note, however, that physically inspecting the ignition coil is not done exactly the same across different ignition mechanisms. For guidance, here’s how the inspection might differ for each:

Distributor

With a distributor-based ignition system, you’d want to inspect the coil’s connections to the distributor cap. Look for signs of corrosion, poor connections, or wear on the distributor cap’s terminals. Also, ensure the ignition coil is securely mounted near or on the distributor. Inspect the distributor itself for any wear or damage.

Distributor-Less

This mechanism (where individual ignition coils are located near each spark plug) focuses on inspecting the condition of each individual ignition coil. Examine the coil’s wiring, connectors, and housing for any damage. Since each coil is independent, ensure they’re properly mounted on their respective spark plugs and look for signs of wear or damage on the coil boots.

Coil-on-Plug

For coil-on-plug systems, you’d want to examine the ignition coils directly mounted on each spark plug. Check the wiring, connectors, and coil housing for any issues. Verify that each coil is securely fastened to its ‘partner’ spark plug and that the coil boots show no indications of damage or loose connections.

4. Detach the Spark Plug Cables.

If you haven’t spotted or ruled out mounting or integrity issues at this stage, then proceed with examining your ATV’s spark ignition. To do this, firmly grasp the boot at the end of each wire and gently twist it while pulling it away from the ignition coil. Make sure to hold the boot itself (NOT the wire) to avoid damaging the wire’s internal connection.

5. Use Spark Testers or Test Lights.

Utilizing these specialized tools provides the most straightforward method for testing a potentially malfunctioning ignition coil. These tools have broad compatibility and are suitable for both traditional distributor systems and contemporary coil layouts. When connected to the wiring, these testers directly demonstrate the flow of charge, streamlining the testing process.

6. Gauge Primary Resistance Readings.

If straightforward methods don’t work, revert to testing the primary and secondary ignition or windings as customary. Starting with primary resistance, use a digital multimeter like a Fluke 28 II Rugged Digital Multimeter (view on Amazon) set to the Ohms mode. Attach the positive (red) lead of the multimeter to the positive terminal of the coil and connect the negative (black) lead to the coil’s negative terminal.

With this process, your aim is to obtain a reading that aligns with the designated range for your ATV. Any measurement that deviates from the OEM-prescribed range — whether excessively low or high — could signal a break in continuity or a potential short circuit in the primary winding. However, be warned — bad ignition coils can still pass this test (and even the secondary resistance one!).

7. Do the Same for Secondary Resistance.

If primary resistance readings check out, proceed with measuring secondary resistance. Using the same tool and settings, follow the same process you did for the primary ignition. The only difference would be connecting the multimeter’s positive lead to the coil’s positive terminal and the negative lead to the spark plug wire socket.

Outlier values typically indicate comparable issues to those linked with abnormally high or low primary resistance. If left unaddressed, these complications can result in symptoms like intermittent sparking, misfiring, and compromised engine performance.

8. Check for Circuit Interruptions and Shorts.

If either or both the primary and secondary resistance readings exceed their specified ranges, you’ll need to test for current overloading or discontinuity in the ignition coil. Depending on the outcome, this can go two ways — a short circuit test for low resistance readings or an open circuit test for high resistance readings.

Utilizing the continuity or diode mode on a digital multimeter, check for potential short circuits within the ignition coil. Attach the positive lead to the coil’s positive terminal. Connect the negative to the negative terminal. You wouldn’t want to hear any sound while doing this step (let alone a beeping one), as that would confirm a short circuit.

Conversely, test for an open circuit using the same multimeter settings by placing the positive lead on the coil’s positive terminal and the negative lead on the spark plug wire socket. This time around, you’d want to hear beeping to signify a good continuity and a complete circuit.

9. Do a Component Swap.

If you’re confused about which component is at fault or what the preceding tests signify, I recommend swapping parts to determine if the probable culprit is the spark plug or the ignition coil.

You can accomplish this by linking the suspected ignition coil to a fresh plug with new wiring. If ignition remains absent, the issue is likely with the coil. Alternatively, you can individually disconnect the wires from each cylinder. If the engine’s idle RPM remains unchanged, it indicates that the coil pertaining to that cylinder is deteriorating.

Of all the ignition coil layouts that your ATV could have, a coil-on-lug system offers the least difficulty. Changing defective parts in ATVs with such a setup is a breeze since a spark plug has its own top-mounted ignition coil.

Older configurations aren’t necessarily more tedious per se, although they may entail removing the engine casing to access. The bigger challenge with these layouts isn’t the layout itself but whether or not your ATV has an ignition coil pack.

10. Examine the Spark Plug Wires.

If you’ve reached this point in the guide, you probably have normal current flow and continuity but are still dealing with an ignition coil issue. It’s time to check on the spark plug wires and other relevant electrical components. Chances are that your ATV’s spark plug wires are damaged, frayed, or excessively worn. In such cases, replace any wire in poor condition.

After you finish testing the ATV ignition coil and related electrical parts, checking them, and carrying out any needed fixes or replacements, reattach the spark plug wires to their corresponding coil terminals. Refer to your notes from the preceding steps (or if you’ve made any labels) when replacing the plugs, and ensure the connections are secure and correctly fitted.

11. Test Ignition and Check for Spark.

Reconnect the ignition coil and spark plug, then start your ATV and observe its performance. If the engine runs smoothly (free from misfires or hesitation), it’s a positive sign that the ignition coil is functioning properly.

Even so, I still strongly recommend confirming spark output at the plugs just to be sure. Doing so confirms the health of internal wiring and external electrical components tied to your four-wheeler’s ignition system.

To verify spark production, remove an engine spark plug and reconnect its wire. Ground the spark plug to the engine block using insulated pliers, and crank the engine while noting any prominent sparks at the electrode. The expectation is that you should get a good, strong spark — any deviation from this outcome may warrant replacing your spark plugs.

12. Seek Professional Assistance.

If you’ve exhausted all the steps mentioned here without success, I recommend consulting a professional mechanic or technician. Their specialized expertise and equipment can effectively diagnose and address complex ignition system issues that you may not have been able to uncover during your troubleshooting and diagnostic processes.

Tools for Testing:

• Diagnostic scan tool (view on Amazon)
• Digital Multimeter
• Voltmeter
• Spark tester or test light
• Measurement probes
• Insulated pliers
• Wrenches or screwdrivers
• Spark plug socket
• Safety gear
• Replace parts
• Battery charger or maintainer (view on Amazon)

Conclusion — How to Check Bad ATV Ignition Coils

Knowing how to tell if the ignition coil is bad on an ATV and what to do to rectify its condition can save you from potential performance issues and breakdowns. That said, I cannot overstate how crucial regular inspection and upkeep of the ignition coil is to the overall health of your ATV’s power mill.

If you encounter any of the symptoms mentioned here, following the testing steps can help you pinpoint the issue and decide on the necessary repairs or replacements. But at any point that you’re unsure about any step, I recommend reverting to your owner’s manual for OEM-recommended procedures. In like manner, seeking assistance from a professional mechanic or technician will tremendously help.