TEST 2: Making Sure The Ignition Coil Is Getting Power
OK, you're here because in TEST 1 you got a no-spark result from one of several ignition coils. The next step is to verify that that ignition coil or coils are receiving power.
The power the ignition coils receive is in the form of 10 to 12 Volts DC. In this section, we'll check for the presence of this voltage using a multimeter.
NOTE: Be careful not to damage the female terminal (of the connector) with the multimeter test leads, or you'll need to replace the connector.
Let's get testing:
- 1
Disconnect the ignition coil that did not spark from its 2-wire connector.
- 2
Place your multimeter in Volts DC mode.
- 3
Connect the black multimeter test lead to the battery negative (-) terminal.
- 4
Gently probe the female terminal of the connector that connects to the wire labeled with the number 2 (see photo above) with the red multimeter test lead.
- 5
Have your helper turn the key to the ON position.
- 6
You should see 10-12 Volts on your multimeter.
Let's take a look at what your test results mean:
CASE 1: The multimeter registered 10-12 Volts (or the test light lit up). This test result tells you that the power circuit is OK and is delivering voltage.
The next step is to test the Switching signal circuit, go to: TEST 3: Making Sure The Ignition Coil Is Getting Its Activation Signal.
CASE 2: The multimeter DID NOT register 10-12 Volts (or the test light DID NOT light up). This test result confirms that the power circuit has a problem.
This result eliminates the COP ignition coil as the source of the misfire condition. The power circuit is shared by all of the COP ignition coils.
TEST 3: Making Sure The Ignition Coil Is Getting Its Activation Signal
OK, you're here because you have confirmed that the ignition coil is not sparking and that 12 Volts are present. The next step is to verify that the ignition coil's is receiving the switching signal from the fuel injection computer. We'll be using an LED light.
Testing for the Switching signal can be done with the ignition coil connected or disconnected to its connector. The method I recommend to use is with it connected to its connector and with a wire-piercing probe (you can see what this tool looks like here: Wire-Piercing Probe).
The other method is to unplug the ignition coil connector and insert the male spade terminals of the LED into the connector's female terminals. If you go this route, keep the following in mind:
- The red wire of LED goes into the female terminal that connects to the red wire of the connector. This wire is labeled withe the number 2 in the photo above.
- The black wire of the LED goes into the female terminal of the wire labeled with the number 1.
NOTE: If you do insert the LED wires into the terminals, make sure that whatever size terminal you insert into them does not open them up. If this happens, you're going to create yourself a major headache.
These are the test steps:
- 1
Connect the black lead of the LED light to the wire labeled with the number 1.
- 2
Connect the red lead of the LED the battery positive (+) terminal.
- 3
Have your helper crank up the engine as you observe the LED light.
- 4
The LED light should flash ON and OFF the whole time the engine is cranking and running.
Let's take a look at what your test results mean:
CASE 1: The LED light flashed ON and OFF. This test result confirms that the Switching signal is present. This result also indicates that the COP ignition coil on your Ford pickup is bad and needs to be replaced.
CASE 2: The LED light DID NOT flash ON and OFF. Re-check all of your connections and repeat the test again.
If still no flashing ON and OFF, then this results eliminates the ignition coil as the source of the no-spark condition/misfire, since without the Switching signal the ignition coil will not work.
There are several possible causes for this that I've seen time and time again with the most common being: An open-circuit problem in the wire that feeds the Switching signal between the fuel injection computer and the COP ignition coil. The second most common: A fried fuel injection computer. Although testing these two conditions are beyond the scope of this article, you have at least eliminated the ignition coil itself as the cause of the problem.
What's The Switching Signal: The 'switching signal' really isn't a physical signal, the term is used to describe how the fuel injection computer opens and closes the Primary Current's (flowing thru' each ignition coil) path to Ground. It's this action that makes the ignition coil fire off spark.
This 'ON/OFF' action can be measured so many different ways and with different types of diagnostic equipment. Using a LED is a simple and inexpensive way of verifying the existence of this signal.
Why is the fuel injection computer providing this signal and not an ignition control module? Well, it's because the ignition control module function is inside the computer itself on this type of Ford Coil-On-Plug ignition system. Therefore, one of the two wires in each of the ignition coil's connector goes straight the fuel injection computer, although they do not share the same circuit.
TEST 4: Checking For Leaking Oil/Anti-Freeze
If all of the ignition coils fired off spark in TEST 1 and yet your Ford pickup is experiencing a misfire condition, then the most likely causes are:
- The spark plug boots spark plugs have developed carbon tracks.
- The spark plugs and spark plug boots are swimming in engine oil or anti-freeze (from a leaking intake manifold gasket).
- Both of the aforementioned conditions.
All of these conditions are a very common occurrence in this type of Ford Coil-On-Plug ignition system.
If the spark plug boots spark plugs are swimming in engine oil, it's usually due to the valve cover gasket leaking oil into the spark plug tubes. This oil will cause the ignition system to misfire and/or cause carbon tracks to form as the spark cooks the oil. The solution here is to replace the valve cover gaskets along with the spark plugs and ignition coil boots.
If the intake manifold gasket (which is made out of plastic) is leaking anti-freeze into the spark plug tubes, this will cause your Ford pickup to misfire. The solution here is to replace the intake manifold gaskets along with the spark plugs and ignition coil boots.
In the image above, you'll see what a carbon track looks like on the spark plug boot and on the spark plugs. The next step is to remove the spark plugs and spark plug boots to visually inspect them for carbon tracks and/or to see if the are all oil-soaked or anti-freeze soaked.
If the spark plugs are oil-soaked and/or anti-freeze soaked and/or with carbon tracks, you'll need to replace them all along with the spark plug boots. Failure to replace one without the other will only make the carbon track return and/or continue to misfire still.
Now, if no carbon tracks are visible on any of the spark plugs, or spark plug boots, then the ignition system is not the cause of your misfire condition. I would check engine compression and the fuel injectors among several things. Go to: Other Common Causes Of A Misfire.
Other Common Causes Of A Misfire
Over the past few years I've noticed a few other things that can cause a misfire code to set that are not caused by the ignition coil itself having gone bad. Some of these have already been covered in the article:
- The fuel injector connector's locking tab is broken. This is a very, very common problem with all Ford vehicles. So, if you have a broken fuel injector connector locking tab, you've probably have found the cause of the misfire!
- The ignition coil connector's are not making a good solid contact with the male spade terminals of the ignition coil. This is the result of human error and the most likely cause is that someone inserted something into the female terminals (of the ignition coil connector) that was bigger/thicker than the male spade terminals that fit into them. This has caused the female terminals (of the ignition coil's connector) to open up permanently and causing a full-time or intermittent false contact condition.
- An open in the wiring has developed somewhere in the wiring-harness that does not let the Switching signal thru'. This is also normally caused by human error after an engine replacement.
- Anti-freeze or engine oil leaking into the spark plug tube and drowning the spark plug and spark plug boot.
- The ignition coil's connector's locking tab has broken. This locking tab is the one that makes sure the connector does not become un-plugged from the ignition coil. This tab usually breaks when the ignition coil is disconnected, either to replace it or the spark plugs.
Case Studies
In this section, is input and feedback from all of the folks who have had a similar issue with their vehicle and found a solution. If you're one of them, thank you for sharing your experience with all of us!
If you want to share your repair and/or diagnostic experience, you can use the contact form below.
Real Life Case Study 1:
Vehicle: 1998 Ford Crown Victoria 4.6L
Trouble Codes: P0300 after washing engine at car wash.
Complaint: “...Anytime I would drive it and give it gas, the engine would miss big time...”
Test Notes: “...What helped me nail down the problem was doing the cylinder balance test, the P0300 codes says they are all missing but it was only two of tehm. The two cylinders were #7 and #5. I took out the plugs and the cop coils and they were wet with water. Man, i cleaned them and dried them like 3 times and also blew out the water in the plug wells and the dang missing would not go away. I knew the coils were good cause they were sparking according to your test with a spark tester...”
“...On the balance test, i didn't use a vacuum gague like you ask, i didn't have one, just unplugging the injectors was enough to tell the difference...”
Repair: REPLACED ALL SPARK PLUGS AND BOOTS “...After pulling my hair out for a few hours, i decided to just replace the spark plugs and the two coil boots. This cured the problem. Since i got the whole engine wet, i decided to go back to the AutoZone and get the rest of the spark plugs and cop boots. Dude, thanks for showing how to do the balance test, it saved my butt. I have learned my lesson, i will never wash an engine again! I did not replace any of the cop coils... ”
Courtesy of: J. Tims
Real Life Case Study 2:
Vehicle: 1997 Ford F150 5.4L
Trouble Codes: P0306.
Complaint: “...Misfire...”
Test Notes: “...I had replaced the ignitioncoil for cylinder 6 two times. Both ignition coils I bought brand new (one from Autozone and the other from Orellys). I though maybe I had bought a defective part the first time anyway, I found your website and did the spark test and no spark. The test that finally helped was checking the switching signal with an LED that I bought at AutoZone...”
“...Prior to finding your tests, I had done a compression test figuring maybe the rings were bad but the compression of #6 was almost the same as the rest. Also checked the fuel injector and tested for the injection signal with a noid light and they were good. I even swapped out the injector with another just in case but it didn't improve a thing...”
Repair: REPAIRED SHORT IN COP COIL WIRE “...I'm no professional mechanic (but i can turn a mean wrench) and wiring problems have always stumped me so I took it to my buddy at his mechanic shop. I told them I was not buying another coil because I already knew that was not the solution. The guys were able to find out that one of the 2 coil wires had a short and that was the reason the cop coil was not working. It was the wire that feeds the activation signal (which you call the switching signal) to the coil. I got it fixed and problem solved. Even though I didn't fix it myself your write up was able to guide me in the right direction. Thank you and with this email I just wanted to pass on my experience to others... ”
Courtesy of: C. T.
More 4.6L, 5.4L Ford F150, F250, And F350 Tutorials
There are quite a few 4.6L, 5.4L V8 F-Series pickup 'how to' tutorials and wiring diagrams you can find here:
E-Series Vans: You can find all of the available tutorials and wiring diagrams for the 4.6L and 5.4L V8 E-Series vans in this index:
- 4.6L, 5.4L Ford E150, E250, And E350 Index of Articles (at: troubleshootmyvehicle.com).
Crown Vic/Grand Marquis: You can find all of the available tutorials and wiring diagrams for the 4.6L V8 Ford Crown Vic and Mercury Grand Marquis in this index:
- 4.6L Crown Victoria And Grand Marquis Index of Articles (at: troubleshootmyvehicle.com).
If this info saved the day, buy me a beer!
