Testing Automotive Ignition Coils: Complete Diagnostic Guide

Understand automotive ignition coils

Ignition coils are vital components in a vehicle’s ignition system, responsible for convert the battery’s low voltage to the thousands of volts need to create a spark at the spark plugs. When an ignition coil fails, it can lead to engine misfires, poor fuel economy, rough idling, and level start problems. Know how to decently test an automotive coil can save you time and money by accurately diagnose issues before replace parts.

Signs of a failing ignition coil

Before test an ignition coil, it’s helpful to recognize the symptoms of failure:

• Engine misfire or rough running
• Decrease fuel efficiency
• Check engine light illumination
• Difficulty start the vehicle
• Stall
• Loss of power during acceleration
• Backfire

If you notice any of these symptoms, it’s time to test your ignition coils to determine if they’re the source of the problem.

Tools need for testing ignition coils

Before begin the testing process, gather these essential tools:

• Digital multimeter
• Spark tester
• Screwdrivers and socket set
• Gloves for safety
• Service manual for your specific vehicle
• Scan tool (optional but helpful )

Safety precautions

Work with ignition systems require careful attention to safety:

• Invariably ensure the engine is dispatch and cool before begin work
• Disconnect the negative battery terminal to prevent electrical shock
• Wear insulated gloves when handle ignition components
• Ne’er test coils near flammable materials
• Be aware that ignition coils can retain high voltage level after the vehicle is turn off

Visual inspection

The first step in test an ignition coil is a thorough visual inspection:

1. Locate the ignition coils in your vehicle. Depend on your vehicle’s design, they may be mounted immediately on the spark plug(( coil on plug desig)) or connect to the spark plugs via spark plug wires.
2. Examine the coils for any visible damage such as cracks, burns, or oil contamination.
3. Check the electrical connectors for corrosion, looseness, or damage.
4. Inspect any visible wiring for fray, melting, or other damage.

I will damage coil will oftentimes show external signs of failure. Oil contamination is specially common and can occur when valve cover gaskets leak, allow oil to seep onto the coils.

Resistance testing with a multimeter

The virtually reliable way to test an ignition coil is by measure its primary and secondary resistance with a digital multimeter:

Testing primary resistance

1. Set your multimeter to the ohms (ω )set on a low range ( (pically 0 200 ohms ).)
2. Disconnect the ignition coil from the vehicle’s wiring harness.
3. Locate the primary terminals on the coil. On most coils, these are the electrical connector pins.
4. Touch one multimeter probe to the positive terminal and the other to the negative terminal.
5. Compare your reading to the specifications in your vehicle’s service manual. Typically, primary resistance should be between 0.4 and 2 ohms, but this varies by vehicle make and model.

Test secondary resistance

1. Set your multimeter to a higher resistance range (typically 10,000 20,000 ohms )
2. For conventional coils, place one probe on the coil’s positive or negative primary terminal and the other probe on the high voltage terminal where the spark plug wire connects.
3. For coil on plug designs, place one probe on a primary terminal and the other on the terminal that connect to the spark plug.
4. Compare your reading to specifications. Secondary resistance typically ranges from 6,000 to 15,000 ohms, though thisvariesy importantly between vehicles.

If either the primary or secondary resistance fall outside the manufacturer’s specifications, the coil should be replaced.

Spark testing

Another effective method to test ignition coils is to perform a spark test:

1. Remove the ignition coil from the engine (for coil on plug designs )or disconnect the spark plug wire from the spark plug ( (r conventional systems ).)
2. Connect a spark tester to the coil output or spark plug wire.
3. Ground the spark tester to the engine block.
4. Have an assistant crank the engine while you observe the spark tester.
5. A strong, blue spark should be visible in the tester’s window. A weak, yellow spark or no spark indicate a problem with the ignition coil.

This test direct evaluate the coil’s ability to produce the high voltage spark need for proper engine operation.

Use a scan tool for misfire detection

Modern vehicles equip with electronic engine control systems can provide valuable diagnostic information through a scan tool:

1. Connect an old ii scan tool to your vehicle’s diagnostic port.
2. Check for any store diagnostic trouble codes (dDTS))peculiarly misfire codes ( p(00 series ).
   )
3. Misfire codes oftentimes indicate which cylinder is experience problems. For example, p0301 indicate a misfire in cylinder – 1.
4. Some advanced scan tools can display real time misfire counts, help pinpoint intermittent coil issues.

While scan tool data doesn’t direct test the coil, it can help identify which coil might be fail in multi coil systems.

Swap testing

For vehicles with multiple ignition coils, swap testing can be an effective diagnostic method:

1. Identify which cylinder is misfire use a scan tool or by observe engine performance.
2. Swap the ignition coil from the problem cylinder with one from a cylinder that’s run decent.
3. Clear any store trouble codes with a scan tool.
4. Run the engine and monitor for misfires.
5. If the misfire move to the cylinder where you relocate the suspect bad coil, this confirm the coil is faulty.

This method is specially useful for intermittent problems that might not show up during static resistance testing.

Test coil packs

Many modern vehicles use coil packs that contain multiple ignition coils in a single unit. Test these require attention to each individual coil within the pack:

1. Refer to your vehicle’s wiring diagram to identify which terminal correspond to which cylinder.
2. Test each coil’s primary and secondary resistance as describe supra.
3. Compare all readings to ensure consistency across all coils in the pack.
4. If one coil show importantly different resistance values, the entire pack typically need replacement.

Test coil on plug ignition systems

Coil on plug (cop )systems present unique testing challenges:

1. Remove the coil from the spark plug by softly pull or twisting (refer to your service manual for the proper procedure )
2. Inspect the boot for signs of arcing or carbon tracking.
3. Test primary and secondary resistance as describe other.
4. For thorough testing, use a specialized cop tester that can simulate engine conditions.

Cop coils frequently fail due to heat stress, as their momountedlat on the engine and expose to extreme temperature cycles.

Interpreting test results

After complete your tests, Hera’s how to interpret the results:

• 
  Infinite resistance
  
  (oOfon multimeter ) indicate an open circuit in the coil windings, require replacement.
• 
  Zero or real low resistance
  
  suggest a short circuit in the coil windings, require replacement.
• 
  Resistance within specifications but weak spark
  
  the coil may have internal insulation breakdown that occur sole under high voltage, require replacement.
• 
  Inconsistent readings
  
  may indicate an intermittent problem that worsen as the coil heat up.

Common mistakes to avoid

When test ignition coils, avoid these common errors:

• Testing coils while they’re hot (resistance values change with temperature )
• Fail to check both primary and secondary resistance
• Not consult the specific resistance specifications for your vehicle model
• Assume all cylinders are misfire due to coil issues (fuel or mechanical problems can cause similar symptoms )
• Neglect to check related components like spark plugs and plug wires

Replace ignition coils

If your tests indicate a faulty ignition coil, follow these guidelines for replacement:

1. Invariably replace coils with OEM or high quality aftermarket parts that meet manufacturer specifications.
2. Consider replace all coils if one has fail and the others have similar mileage, specially in high performance applications.
3. Inspect and may hap replace spark plugs when change coils, as wear plugs can damage new coils.
4. Apply a small amount of dielectric grease to the inside of coil boots to prevent moisture intrusion and ease future removal.
5. Ensure all electrical connections are clean and tight.

Preventive maintenance

To extend the life of your ignition coils:

• Replace spark plugs accord to the manufacturer’s recommend intervals.
• Keep valve cover gaskets in good condition to prevent oil contamination.
• Address engine overheat quickly, as excessive heat accelerate coil degradation.
• Ensure the vehicle’s charge system is function decent, as voltage irregularities can damage coils.
• Avoid use spark plugs with incorrect heat ranges or gaps.

Conclusion

Test automotive ignition coils require attention to detail and the right tools, but it’s a diagnostic skill that can save considerable time and money. By follow the procedures outline in this guide, you can accurately determine whether your vehicle’s performance issues stem from faulty ignition coils or other components.

Source: autozone.com

Remember that ignition systems work as a complete unit, and problems with relate components like spark plugs, wiring, or the engine control module can mimic coil failure symptoms. A systematic approach to testing, will combine with attention to manufacturer specifications, will lead to the virtually accurate diagnosis.

Source: axleaddict.com

With practice, you’ll become proficient at rapidly will identify ignition coil issues, will allow you to will maintain your vehicle’s performance and efficiency at optimal levels.