First Test: Spark Test
Here are the step by step tests for testing the majority of the Coil-On-Plug ignition systems that have ignition coils with three wires (circuits) in the connector. So whether it's a Ford, a Chevrolet, a Mazda, a Suzuki, a Mitsubishi or whatever in the USA, or Europe or South or Central America, or where ever on the planet, these easy tests work.
The basic flow of testing is as follows:
- Test for spark first.
- Test for power (12 Volts) and Ground second.
- Test for the Triggering signal third.
Following this recommended testing sequence will help you to diagnose the Coil-On-Plug ignition coil faster and efficiently.
How The Spark Test Is Done
As you can see in the photo above, testing for spark is achieved by using a spark tester. The Coil-On-Plug ignition coil to be tested is removed from its place and tester is attached to it. An assistant then cranks up the engine. The spark tester is then observed to see if spark jumps across its air gap. Easy stuff, no?
Using a regular spark plug instead of a spark tester for this test is a no no. You ARE NOT going to get a true result you can trust. Only a dedicated spark tester will stress test the Coil-On-Plug ignition coil. And only the result of this spark tester can be trusted.
I don't recommend using just any type of spark tester. There is only one that I use, only one that I trust, and the only one I recommend: the HEI spark tester. This spark tester isn't expensive and more importantly can be bought just about anywhere (online, auto parts stores, mechanic tool trucks, etc.) It usually costs around 9 to 10 dollars (us).
If you want to find out more about how this tool works, I recommend the following article (within this site): The HEI Spark Tester (The Best Spark Tester On The Market)..
Interpreting The Results Of The Spark Test
You'll get one of two results with the spark test. Either you'll get spark or no spark. That's it!
You got NO SPARK. The most common result of all of the tests (in about 90 percent of the time) is that the Coil-On-Plug ignition coil is indeed bad.
Yet, getting a no-spark result does not necessarily condemn the Coil-On-Plug ignition coil to the trash can. There are two more things that we have to check for. One: the power and Ground circuits have to be checked for 12 Volts and Ground respectively. Second: the Triggering signal's presence has to be verified on the Triggering circuit.
By testing for the presence of these signals we can be absolutely certain that we're gonna' spend the money on a solution and not a guess.
You got SPARK- If you get a good and continuous spark on the spark tester as the engine was being cranked, then that Coil-On-Plug ignition coil is working fine.
If you're diagnosing a misfire condition. A carbon track on the coil's boot or on the spark plug may be diverting the spark. I recommend the following article to learn more about carbon tracks Ignition Misfire A Case Study Of A Dodge Neon.
Let's continue and find out about testing the other signals that the Coil-On-Plug ignition coil needs to create spark.
Testing The Power And Ground Circuits
On the previous page I mentioned that there are three basic things that need to be tested and/or verified on a Coil-On-Plug ignition coil:
- Spark. This is done with a spark tester.
- Power (12 Volts) and Ground.
- A Triggering signal.
In this part of the article, we're gonna' take a look at how to test the power and Ground circuits.
Power And Ground Circuits
The power and Ground circuits of the Coil-On-Plug ignition coil (type with three wires in the connector) have to be tested to find out the real reason you got a no-spark result on your spark tester.
Usually these circuits are fine and are providing their respective signals. And it's just that the Coil-On-Plug ignition coil is bad. But by testing these circuits you're making absolutely sure you're gonna' spend money on a solution and not a guess.
The cool thing about testing the power and Ground circuits is that it doesn't require a lot of time nor are the tests difficult to do. You can use a multimeter or a 12 Volt test light for these tests. I prefer the multimeter, but have used the test light also with the same results.
You can probe the front of the female terminals of the connector or (like what I do) use a wire-piercing probe to test the wire itself (like in the photo above).
If you probe the front of the connector, you have to keep in mind the following IMPORTANT suggestion: You can not force something that is bigger or thicker than the male spade terminal that fits into it to test for power or Ground.
Testing The Power Circuit
The fastest way to identify the power and Ground circuits is using a wiring diagram. If you don't have one you'll have to find out by trial and error as you probe each circuit.
The power circuit is tested with the Key On Engine Off (KOEO). Place one end of your multimeter or test light on the battery negative (-) terminal and with the other end, probe the Power circuit. Turn the key to the RUN position. If the power circuit is OK, the multimeter will show 12 Volts or the test light will light up. Here are the possible results:
- You got 12 Volts on the power circuit
- Good, this is a good sign. The next step is to check the Ground circuit of the COP ignition coil connector that you're testing.
- No power in only one ignition coil
- Without 12 Volts, the Coil-On-Plug ignition coil will not work, thus you have just eliminated that specific ignition coil as the source of the fault. Replacing the ignition coil with a new one will only be a waste of time and money since, without power the new one will not spark.
- Since the power circuit is shared by all of the coils on the majority of Coil-On-Plug ignition systems. The most likely cause will be an open-circuit problem in that ignition coil's power circuit.
- You'll have to consult your repair manual's wiring diagrams to make sure how everything is wired up.
- After repairing the short, re-do the spark test to verify the ignition coil is now working.
- No power at any ignition coils
- The fuse or relay that supplies this voltage is blown or bad.
- You'll have to consult your repair manual's wiring diagrams to see where this fuse and/or relay is located and replace as necessary.
- After replacing the blown fuse or the defective relay. Retest the ignition coil.
Testing The Ground Circuit
The Ground circuit is tested with the key ON or OFF. It doesn't matter because this is a Chassis Ground. Place one end of your multimeter or test light on the battery positive (+) terminal and with the other end, probe the Ground circuit. If the Ground circuit is OK, the multimeter will show 12 Volts or the test light will light up.
- You got Ground
- Good, now the next step is to verify that the Coil-On-Plug ignition coil is receiving the Triggering signal. This info belongs to the next section of this article.
- No Ground in only one ignition coil
- Without this Ground, the Coil-On-Plug ignition coil will not work, thus you have just eliminated that specific ignition coil as the source of the fault. Replacing the ignition coil with a new one will only be a waste of time and money since, without Ground the new one will not spark.
- Since the Ground circuit is shared by all of the coils on the majority of Coil-On-Plug ignition systems. The most likely cause will be an open-circuit problem in that ignition coil's Ground circuit.
- You'll have to consult your repair manual's wiring diagrams to make sure how everything is wired up.
- After repairing the short, re-do the spark test to verify the ignition coil is now working.
- No Ground at any ignition coils
- This usually happens thru' human error in most cases and is a very rare thing. Usually the engine was replaced and this Ground was not re-attached.
- You can Ground this circuit with a jumper wire. Jumpering to Ground just one Coil-On-Plug ignition coil should provide Ground to all of them (consult your repair manual's wiring diagrams to be sure).
- With this jumper wire to Ground attached, crank the vehicle.
- If in fact the Ground circuit does have an open-circuit problem, this (the jumper wire to Ground) should make the vehicle start, or at least get the ignition coil to spark.
- Repair the open-circuit problem and retest for spark or retry starting the vehicle.
Alright, let's find out how to test the Triggering signal in the next page.
