How To Test Small Engine Ignition Coil With Multimeter?

Testing a small engine ignition coil may look challenging, but it is reliable to accomplish it with the right guide. Do you know how?

An ignition coil is actually a pulse-type transformer winded with two coils called primary and secondary and durably coiled over each other.

Testing the ignition coil generally depends on the vehicle model, current engine, and the surrounding conditions.

Therefore it is necessary to be aware of the entire process of how to test the ignition coil in the best possible way.

Are you confused? Well, don’t worry! We have got you covered with our detailed guide on how to test small engine ignition coil with multimeter. Let’s get right in!

Testing the Ignition Coil

Before testing the ignition coil, you need to know that whether the loop is good or bad. Seriously it’s crucial if you want the testing to be done successfully.

Moreover, it is a simple process, and the most common use is of a digital multimeter for effective checking. So? You can opt for these tests at home.

Tools you need

• A test light and a spark plug
• Heat gun
• Wrench
• Socket set
• Resistance specifications
• Digital multimeter

Know Specs

Before going towards the specs, it is crucial to know the resistance specification for both the specific ignition coils’ primary and secondary windings.

From where will you get this information? Well, basically, from the user manual as you will need this specification when compiling your results.

At last, you will have to compare the specifications with your results. Got it?

Test the Coil’s Primary Resistance

To be honest, you can go to test the coil while it’s mounted on your vehicle. But do it when you have adequate access to it, or otherwise, you can remove it.

Procedure:

• Unplug the high voltage and the connector that’s connecting the coil and the distributor.
• Remember to unscrew the mounting bolts so the ignition coil is removed from your vehicle.
• Examine the wires or the connectors for any damage, corrosion, and even dirt.
• Ensure to check the coil whether there is any physical damage or not.
• All these conditions prevent the coil from generating the required voltage.
• Set the digital voltmeter to shallow settings or switch it to the auto-range mode.
• Connect the leads only across the primary terminals as one across the positive terminal and the other along with the negative terminal.

Water Spark System:

Here’s what you need to do!

• Check the ignition coil thoroughly if there any physical damage. You know what? Damage prevents the ring from generating the required voltage of the plugs.
• Set the DMM correctly to a low setting.
• Connect the leads.

Results:

What’s the catch, by the way? You have to compare the reading with the specification mentioned in the user manual. Measure them accordingly!

• A typical primary resistance generally ranges from 0.3 to 1 ohm.
• Now, what happens if the resistance is below the specification mentioned above? Probably the primary winding is shorted, and you need to replace the coil.
• But if the resistance dramatically exceeds the standard range, then you have to replace the coil too!
• Do you know what the infinite resistance on the meter indicates? Let us tell you! That’s because the primary winding has got an electrical open. You will need to replace the coil here as well.

Test the Ignition Coil’s Secondary Resistance

Procedure:

• Set the DMM to auto mode range or a 20K ohms.
• Connect one part of the DMM leads to the BAT terminal while the other leads to the coil tower or the second terminal.
• In a few ignition coils, the secondary terminal is connected to the coil’s frame.
• If this happens, you have to connect leads across the coil’s frame and the secondary terminal instead of the primary one.

Waste Spark Systems:

What to do with such systems? Well, connect the ohmmeter leads across both the secondary terminals. These terminals are on one side of your coil body.

Coil on Plug Systems:

Don’t forget to consult the repair manual by the manufacturer to indicate the terminals.

Results:

Compare the results to the user’s manual.

• A typical secondary resistance usually ranges from 6000 to 12000 ohms.
• What if the reading is below your specification? It indicates that the secondary winding is shortened, and you have to replace the coil.
• But if there is infinite resistance, it determines electrical open in your windings.
• If the reading is slightly higher than the manual specification, it indicates too much resistance in the coil’s winding.

Testing the Ignition Coil for other Voltage Leaks

Sometimes the coil tests are okay, but the problem is with the other faults, such as lousy insulation and other internal issues between them during the coil operation.

This test will help you find such potential problems.

What do you need?

At least to accomplish this test, you will require:

• Spark plug with a high voltage or a low voltage
• Test light

Procedure:

• Firstly connect the spark plug effectively to the ignition coil’s output terminal. Ensure to ground the plug.
• Some systems have more than one coil, so you have to remove the fuel systems fuse and prevent the system from starting.
• Crank the engine, so it is sufficient enough to inspect the spark’s condition.
• The spark plug will fire a bright blue spark.

But if you saw a weak spark with orange color or no spark, you will have to go for the next test. Here’s the procedure for it!

• Connect the test light correctly between the ground and the ignition coil negative terminal. Ensure to do it accurately.
• There may be a need for a copper wire strand along with a test light. That’s because it can adhere to the negative terminal to make sure that the connector is plugged in correctly during the test.
• On the ignition key! On many applications, test light needs to be on, but in a few, they are not.
• Check the ignition system mentioned in your manufacturer’s manual.
• If the test light is off, it represents an open between the BAT terminal and the switch in the ignition coil.
• While connecting the test light, you can crank the engine.
• What’s the catch? Well, if the test light lightens up, it’s an indication that the primary circuit in the coil is working correctly. But don’t forget the ring is wrong.
• What if the light doesn’t flash? Here you need to check whether there a voltage at the terminal or not.
• If there is no voltage, see the ignition switch or the corresponding circuit side. In many applications, there’s a problem with the position sensor too.
• But if there is voltage, then check the ignition system module correctly.

The Bottom Line

Testing an ignition coil is really crucial whenever we talk about this elegantly designed transformer.

But wait! Is it confusing? Does it require lots of tools?

To be honest, NO, it is a quick and straightforward process to test the ignition coil using a multimeter. You only need to follow the proper steps to make it happen.

After going through the entire procedure and mentioning everything in detail, we hope to achieve this testing reliably at home. Ensure to follow the steps accurately!