Ignition coils are an essential part of any internal combustion engine. They are responsible for creating the spark that ignites the air-fuel mixture in the cylinders. A faulty ignition coil can cause a variety of problems, including engine misfires, reduced power, and increased fuel consumption. If you suspect that your ignition coil may be faulty, it is important to test it as soon as possible.
One way to test an ignition coil is to use a multimeter. A multimeter is a versatile tool that can be used to measure a variety of electrical properties, including voltage, current, and resistance. To test an ignition coil with a multimeter, you will need to set the multimeter to the ohms setting. Once the multimeter is set, you will need to connect the probes to the terminals of the ignition coil. The reading on the multimeter will tell you the resistance of the ignition coil.
If the resistance of the ignition coil is within the manufacturer’s specifications, then the ignition coil is most likely good. However, if the resistance of the ignition coil is outside of the manufacturer’s specifications, then the ignition coil is most likely faulty and will need to be replaced.
Verifying Coil Resistance
A multimeter is a handy tool for diagnosing ignition coils. By measuring the coil’s resistance, you can determine if it is within specifications and functioning properly. Here are the steps on how to verify coil resistance using a multimeter:
1. Disconnect the coil from the ignition system. Ensure the ignition is turned off and the vehicle is cool. Locate the ignition coil and disconnect it by unplugging the electrical connector and removing any bolts or clamps holding it in place.
2. Set the multimeter to ohms. Most multimeters have a dial or button to select different measurement ranges. Set the multimeter to the ohms range, typically denoted by the Greek letter omega (Ω).
3. Identify the coil terminals. The ignition coil will have two terminals: the primary terminal (usually connected to the ignition module) and the secondary terminal (connected to the spark plug). Use the multimeter probes to touch each terminal.
4. Read the resistance. The multimeter will display the resistance value in ohms (Ω). Compare the measured resistance to the specifications for the ignition coil. If the resistance is outside the specified range, the coil may be faulty and require replacement.
Typical Resistance Values for Ignition Coils:
| Ignition Coil Type | Resistance Range |
|---|---|
| Standard Ignition Coil | 0.4 – 2.0 ohms (Primary) |
| High-Performance Ignition Coil | 0.5 – 1.5 ohms (Primary) |
| Direct Ignition Coil | 5,000 – 15,000 ohms (Primary) |
Note: Resistance values may vary depending on the specific coil manufacturer. Refer to the manufacturer’s specifications for the correct values for your coil.
Measuring Primary Circuit Resistance
The primary circuit of an ignition coil consists of the coil windings and the primary terminals. To test the primary circuit resistance, follow these steps:
1. Set your multimeter to the ohms (Ω) setting.
2. Connect the multimeter probes to the primary terminals of the ignition coil. One probe should be connected to the positive terminal, and the other probe should be connected to the negative terminal.
3. Read the resistance value on the multimeter display. The resistance value should be within the specified range for the ignition coil. The specified range can be found in the ignition coil’s technical specifications.
4. If the resistance value is outside of the specified range, the primary circuit may be damaged. The ignition coil may need to be replaced.
Here is a table with the typical resistance values for different types of ignition coils:
| Ignition Coil Type | Primary Circuit Resistance (Ω) |
|---|---|
| Standard Ignition Coil | 0.5 – 2.0 |
| High-Performance Ignition Coil | 0.2 – 0.8 |
| Direct Ignition Coil | 0.1 – 0.5 |
Testing Secondary Circuit Resistance
Step 3: Measuring Secondary Coil Resistance
To measure the secondary circuit resistance, follow these steps:
a) Finding the Ignition Coil Terminals:
- Locate the ignition coil, usually situated near the engine.
- Identify the terminals on the coil: typically, there will be two terminals (positive and negative) for the primary circuit and a single terminal for the secondary circuit.
b) Connecting the Multimeter:
- Turn the multimeter to the ohms (Ω) setting.
- Connect the black (negative) probe to the negative terminal of the primary circuit.
- Connect the red (positive) probe to the secondary terminal.
c) Reading the Resistance:
- The multimeter will display the resistance value in kilo-ohms (kΩ).
- Compare the measured resistance to the specifications provided by the manufacturer. If the resistance falls outside this range, it indicates a faulty coil.
| Resistance Range (kΩ) | Ignition Coil Type |
|---|---|
| 4-15 | Conventional Ignition Coil |
| 5-45 | Electronic Ignition Coil |
| 4-25 | Waste Spark Ignition Coil |
Inspecting Wire and Connectors
Thoroughly inspect all the wiring and connectors associated with the ignition coil. Look for any signs of damage, such as frayed insulation, broken wires, or loose connections. Ensure the connectors are securely plugged into the coil and any other components they connect to. Pay particular attention to the condition of the high-tension wire, as this is prone to degradation over time due to exposure to high voltage and heat.
Checking Resistance Values
| Circuit | Resistance Reading |
|---|---|
| Primary Circuit | 0.5 – 1.5 ohms |
| Secondary Circuit | 5,000 – 25,000 ohms |
Using the multimeter’s resistance setting, measure the resistance of the primary and secondary circuits of the ignition coil. For the primary circuit, disconnect the wiring harness and measure the resistance between the positive and negative terminals. For the secondary circuit, measure the resistance between the high-tension terminal and the negative terminal.
Assessing Continuity
Set the multimeter to the continuity setting. Touch one probe to the positive terminal of the primary circuit and the other probe to the negative terminal. If the coil is functional, the multimeter should beep, indicating continuity. Repeat this process for the secondary circuit, touching one probe to the high-tension terminal and the other to the negative terminal. If there is no continuity, the coil may be faulty and require replacement.
Checking Ignition Module Output
After confirming the presence of voltage at the coil and the ground continuity of the coil, the next step is to test the ignition module’s output. An ignition module is an electronic component that controls the timing and duration of spark delivery to the spark plugs. A faulty ignition module can cause various engine problems, including misfiring, unstable idle, and difficulty starting.
To test the ignition module’s output, you will need a multimeter. Follow these steps:
1. Turn the ignition switch to the “ON” position. Do not start the engine.
2. Connect the multimeter’s black lead to ground (a good ground point on the engine block).
3. Connect the multimeter’s red lead to the positive terminal of the ignition coil.
4. Set the multimeter to the “AC voltage” range.
5. Observe the multimeter reading. The multimeter should display a voltage reading. If the voltage reading is below specifications or zero, the ignition module may be faulty and needs to be replaced.
Utilizing a Test Light for Secondary Circuit
The secondary circuit in an ignition coil is the side that carries the high voltage required to spark the spark plugs. To test the secondary circuit with a test light, follow these steps:
-
Disconnect the spark plug wire from the spark plug.
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Connect the test light’s clip to the engine’s ground.
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Hold the test light’s probe against the spark plug wire connector.
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Have an assistant crank the engine over.
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If the test light flashes, the secondary circuit is intact.
-
If the test light does not flash, there may be a problem with the coil, the wiring, or the spark plug.
| Symptoms | Possible Causes |
|---|---|
| No spark | Defective coil, open secondary circuit, faulty spark plug, or ignition module |
| Weak spark | Worn coil, high resistance in secondary circuit, or fouled spark plug |
| Intermittent spark | Loose connections, bad wiring, or a cracked coil |
To further troubleshoot, check the resistance of the secondary circuit using a multimeter. The resistance should be within the manufacturer’s specifications, which can usually be found in the vehicle’s repair manual.
Verifying Coil Ground
1. Establishing Safe Working Environment
Before beginning any tests, ensure the ignition coil has been completely disconnected from the vehicle’s electrical system and the engine is turned off. Wear insulated gloves for added protection.
2. Discharge Residual Energy
To safely discharge any residual energy, use a spark plug tester or a high-voltage resistor. Insert the tester into the coil and ground it on the engine block. This will help prevent any potential shocks or damage to your multimeter.
3. Connecting Multimeter
Connect the black lead of a digital multimeter to the negative terminal of the battery or a clean ground on the engine. Connect the red lead to the primary terminal of the ignition coil, which is typically labeled with a “P” or “-” terminal.
4. Setting Meter to Ohms
Ensure the multimeter is set to the ohms or resistance setting. This will measure the resistance between the coil primary winding and ground.
5. Reading Resistance Values
The resistance reading should be within the manufacturer’s specifications, typically ranging from 0.4 to 2 ohms for primary coils, and 10-100 ohms for secondary coils. If the reading is significantly higher or lower, it indicates a problem with the coil.
6. Diagnosing Open Circuits
If the resistance reading is infinite or “OL” (open loop), it suggests an open circuit in the coil’s primary winding. This indicates a break or damaged insulation.
7. Identifying Short Circuits
An abnormally low or “0” (short loop) reading indicates a short circuit in the coil’s primary winding. This could be caused by internal insulation breakdown or a faulty coil.
Diagnosing Coil Saturation
Diagnosing coil saturation involves examining the output voltage of the ignition coil under load. If the output voltage drops significantly under load, it indicates coil saturation. Here’s a detailed step-by-step procedure:
1. Connect the Multimeter
Connect the positive test lead of the multimeter to the positive terminal of the ignition coil and the negative test lead to the negative terminal.
2. Set the Multimeter to Voltage Measurement
Set the multimeter to measure DC voltage in the 20V or higher range.
3. Start the Engine
Start the engine and let it idle.
4. Observe the Output Voltage
Observe the output voltage displayed on the multimeter. It should be slightly higher than the battery voltage, typically around 12-14 volts.
5. Connect a Load
Attach a load to the ignition coil, such as a spark plug or a spark gap tester.
6. Re-Observe the Output Voltage
Re-observe the output voltage displayed on the multimeter. If the output voltage drops significantly, below 10 volts or less, it indicates coil saturation.
7. Different Types of Coil Saturation
There are two main types of coil saturation:
- Primary Saturation: Occurs when the primary winding of the ignition coil cannot handle the current flow.
- Secondary Saturation: Occurs when the secondary winding of the ignition coil cannot handle the high voltage buildup.
8. Advanced Testing for Coil Saturation
For more advanced testing, an oscilloscope can be used to further analyze the output waveform of the ignition coil. An oscilloscope can provide a visual representation of the voltage and current flow, allowing for a more in-depth diagnosis of coil saturation issues. The following table summarizes the different values and observations associated with coil saturation:
| Condition | Output Voltage | Indication |
|---|---|---|
| Normal | Slightly higher than battery voltage | No saturation |
| Primary Saturation | Low voltage (< 10V) under load | Primary winding cannot handle current flow |
| Secondary Saturation | High voltage spike, then drop below 10V | Secondary winding cannot handle high voltage buildup |
Interpreting Multimeter Readings
Analyzing the readings on your multimeter is crucial for accurately diagnosing the condition of your ignition coil. Here’s a breakdown of what each reading indicates:
9. Continuity Test
A continuity test determines if there is a complete circuit between two points. Here are the possible outcomes and their implications:
| Reading | Interpretation |
|---|---|
| 0 ohms | Continuous circuit: The coil is not open and has low resistance. |
| OL (open loop) | Broken circuit: The coil is open and has high resistance. |
| < 1 ohm | Short circuit: The coil has very low resistance, indicating a potential short within the winding. |
If you get an OL reading, the coil has a broken circuit and needs replacement. If the resistance reading is < 1 ohm, the coil has a short circuit and should also be replaced.
Troubleshooting Common Issues
Here are some common issues that you may encounter when testing ignition coils with a multimeter:
1. No continuity between the primary terminals
This indicates an open circuit in the primary winding. Check for any breaks in the wire or damage to the terminals. Replace the ignition coil if necessary.
2. No continuity between the secondary terminals
This indicates an open circuit in the secondary winding. Check for any breaks in the wire or damage to the terminals. Replace the ignition coil if necessary.
3. Low resistance between the primary terminals
This indicates a short circuit in the primary winding. Check for any damaged insulation or grounding of the winding. Replace the ignition coil if necessary.
4. High resistance between the secondary terminals
This indicates a short circuit in the secondary winding. Check for any damaged insulation or grounding of the winding. Replace the ignition coil if necessary.
5. Incorrect voltage output from the secondary terminals
This indicates a problem with the ignition coil’s ability to generate the necessary voltage for spark production. Check the coil’s specifications and compare them to the measured output. Replace the ignition coil if necessary.
6. Intermittent operation
This indicates a loose connection or a problem with the ignition coil’s internal components. Check all connections and terminals for tightness. If the problem persists, replace the ignition coil.
7. Overheating
This indicates a problem with the ignition coil’s ability to dissipate heat. Check the coil’s mounting and make sure it is not obstructed. Replace the ignition coil if necessary.
8. Engine misfires
This can be caused by a weak or failing ignition coil. Check the coil’s output and resistance and replace it if necessary.
9. Poor fuel economy
This can be caused by an ignition coil that is not producing the correct voltage or spark energy. Check the coil’s output and resistance and replace it if necessary.
10. Hard starting
This can be caused by a weak or failing ignition coil that is not providing enough spark energy to ignite the fuel mixture. Check the coil’s output and resistance and replace it if necessary.
How To Test Ignition Coil With Multimeter
The ignition coil is a critical component of an engine’s ignition system. It is responsible for converting the battery’s voltage into a high voltage that is necessary to create a spark at the spark plugs. A faulty ignition coil can cause a variety of problems, including hard starting, misfiring, and poor fuel economy.
Testing an ignition coil with a multimeter is a relatively simple procedure. Here are the steps:
1.
Disconnect the negative battery terminal.
2.
Locate the ignition coil. It is usually mounted on the engine, near the spark plugs.
3.
Identify the terminals on the ignition coil. There will be two terminals, a primary terminal and a secondary terminal.
4.
Set the multimeter to the ohms scale.
5.
Touch one probe of the multimeter to the primary terminal and the other probe to the secondary terminal.
6.
The multimeter should read between 5 and 15 ohms. If the reading is outside of this range, the ignition coil is faulty and should be replaced.
People Also Ask
How do you check an ignition coil with a spark tester?
To check an ignition coil with a spark tester, follow these steps:
1.
Disconnect the negative battery terminal.
2.
Remove the spark plug from the cylinder that you are testing.
3.
Connect the spark tester to the spark plug wire.
4.
Ground the spark tester to the engine block.
5.
Have someone crank the engine while you watch the spark tester.
6.
If there is no spark, the ignition coil may be faulty.
What are the symptoms of a bad ignition coil?
The symptoms of a bad ignition coil can include:
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Hard starting
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Misfiring
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Poor fuel economy
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Stalling
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Backfiring
Can a bad ignition coil cause a car not to start?
Yes, a bad ignition coil can cause a car not to start. The ignition coil is responsible for providing the spark that ignites the air/fuel mixture in the cylinders. If the ignition coil is not working properly, there will be no spark and the engine will not start.
