Checking/Testing ignition coils
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Le Mans Master
Joined: Jan 2007
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From: S. FLA :: Professional Devil's Advocate
Checking/Testing ignition coils
Long story short, put on valve cover spacers, had to ghetto rig the driver side coil bracket to make it fit. Shorted out that side and blew the fuse for those coils/fuel injectors. So I reluctantly did some grinding on the valve covers to make them work with the bigger rockers and replaced the fuse. The fuse doesn't blow now but it acts the same way (hard to start). I think I may have blown out one or more of the coils on that side as a few of the coils were sitting on the coil bracket mounts and the valve covers were grounded.
How do I test these things? I tried to do a multimeter test to compare resistance between all the coils but I cannot get any reading out of any of the coils on either side in any sort of configuration.
How do I test these things? I tried to do a multimeter test to compare resistance between all the coils but I cannot get any reading out of any of the coils on either side in any sort of configuration.
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Joined: Oct 2010
Posts: 71
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From: Jonesboro, AR
Long story short, put on valve cover spacers, had to ghetto rig the driver side coil bracket to make it fit. Shorted out that side and blew the fuse for those coils/fuel injectors. So I reluctantly did some grinding on the valve covers to make them work with the bigger rockers and replaced the fuse. The fuse doesn't blow now but it acts the same way (hard to start). I think I may have blown out one or more of the coils on that side as a few of the coils were sitting on the coil bracket mounts and the valve covers were grounded.
How do I test these things? I tried to do a multimeter test to compare resistance between all the coils but I cannot get any reading out of any of the coils on either side in any sort of configuration.
How do I test these things? I tried to do a multimeter test to compare resistance between all the coils but I cannot get any reading out of any of the coils on either side in any sort of configuration.
Ignition Coil Resistance Check
In addition to the test above, you may elect to perform an ignition coil resistance check as confirmation of the coil's condition.
1. Check the ignition coil primary coil resistance by connecting an ohmmeter between the positive (Black wire) and negative (Green wire) terminals on the coil. The resistance should be 0.4 to 0.6 ohms.
2. Check the ignition coil secondary coil resistance by connecting an ohmmeter between the coil output terminal and the ignition coil negative terminal. The resistance should be 5000 to 7200 ohms.
Tech Contributor
Joined: Jan 2007
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From: Dyer, IN
Long story short, put on valve cover spacers, had to ghetto rig the driver side coil bracket to make it fit. Shorted out that side and blew the fuse for those coils/fuel injectors. So I reluctantly did some grinding on the valve covers to make them work with the bigger rockers and replaced the fuse. The fuse doesn't blow now but it acts the same way (hard to start). I think I may have blown out one or more of the coils on that side as a few of the coils were sitting on the coil bracket mounts and the valve covers were grounded.
How do I test these things? I tried to do a multimeter test to compare resistance between all the coils but I cannot get any reading out of any of the coils on either side in any sort of configuration.
How do I test these things? I tried to do a multimeter test to compare resistance between all the coils but I cannot get any reading out of any of the coils on either side in any sort of configuration.
Thread Starter
Le Mans Master
Joined: Jan 2007
Posts: 9,844
Likes: 33
From: S. FLA :: Professional Devil's Advocate
The fuel pump primes to a good pressure; although admittedly I haven't looked at it with the car running. My other thought was possibly gummed up injectors. They are new LS3 injectors and started up good the first time but then they sat for over a year. That's why I wanted to test the coils. If it wasn't that I was figuring fuel injectors may be the issue. I want to send them to FIC injectors anyway to open them up a bit, just wanted to diagnose the issue first though.
I had to tear it down after that first start and checked everything over because the cam bolts backed out shortly after a I started it. I didn't drive it anywhere but at that time it threw a code related to the cam sensor because the cam moved forward. I didn't think that damaged the sensor only because I haven't had any codes related to the cam sensor since that time.
As for new codes, I didn't get any while having it idle for 15-20 minutes along with a few revs.
Thread Starter
Le Mans Master
Joined: Jan 2007
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From: S. FLA :: Professional Devil's Advocate
Looked on my prolink, but found no coil information. Here's a bit of info off Tech, not sure it's valid but tells you the pins.
Ignition Coil Resistance Check
In addition to the test above, you may elect to perform an ignition coil resistance check as confirmation of the coil's condition.
1. Check the ignition coil primary coil resistance by connecting an ohmmeter between the positive (Black wire) and negative (Green wire) terminals on the coil. The resistance should be 0.4 to 0.6 ohms.
2. Check the ignition coil secondary coil resistance by connecting an ohmmeter between the coil output terminal and the ignition coil negative terminal. The resistance should be 5000 to 7200 ohms.
Ignition Coil Resistance Check
In addition to the test above, you may elect to perform an ignition coil resistance check as confirmation of the coil's condition.
1. Check the ignition coil primary coil resistance by connecting an ohmmeter between the positive (Black wire) and negative (Green wire) terminals on the coil. The resistance should be 0.4 to 0.6 ohms.
2. Check the ignition coil secondary coil resistance by connecting an ohmmeter between the coil output terminal and the ignition coil negative terminal. The resistance should be 5000 to 7200 ohms.
Would a timing light setup work to at least test the car when it is running to see if I'm getting good consistent spark?
The car will run it just needs to be "primed" on start. Turn the key for a few seconds, turn if off, then turn it back on and it gurggles a bit from the excess fuel and then levels out.
Tech Contributor
Joined: Jan 2007
Posts: 19,350
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From: Dyer, IN
I found that as well, but I can't seem to get a reading from any of my 3 multimeters.
Would a timing light setup work to at least test the car when it is running to see if I'm getting good consistent spark?
The car will run it just needs to be "primed" on start. Turn the key for a few seconds, turn if off, then turn it back on and it gurggles a bit from the excess fuel and then levels out.
Would a timing light setup work to at least test the car when it is running to see if I'm getting good consistent spark?
The car will run it just needs to be "primed" on start. Turn the key for a few seconds, turn if off, then turn it back on and it gurggles a bit from the excess fuel and then levels out.
Sounds like you do not know where you are at with the fuel pressure. I would not get to distracted by the coil, until you know exactly what your fuel pressure is at key on(and verify no bleed down), and engine running. I assume you have a fuel gauge?
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Joined: Oct 2010
Posts: 71
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From: Jonesboro, AR
Beat me to it Lucky. By the way I figured my problem out. Bad ground at the back at the head. Cleared it right up.
Outclast You do need to check that fuel pressure during startup and see what that tells.
Outclast You do need to check that fuel pressure during startup and see what that tells.
Last edited by bo.benson; Jun 13, 2011 at 02:26 PM.
Thread Starter
Le Mans Master
Joined: Jan 2007
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From: S. FLA :: Professional Devil's Advocate
Yes, you can use a timing light on that plug wire, to make sure it's firing. If the coil was not firing, you would have a flashing check engine light. You can also pull the plug, and verify by the color.
Sounds like you do not know where you are at with the fuel pressure. I would not get to distracted by the coil, until you know exactly what your fuel pressure is at key on(and verify no bleed down), and engine running. I assume you have a fuel gauge?
Sounds like you do not know where you are at with the fuel pressure. I would not get to distracted by the coil, until you know exactly what your fuel pressure is at key on(and verify no bleed down), and engine running. I assume you have a fuel gauge?
The fuel pressures were as follows:
Key to on, primed: 60psi
Cranking: 63-65psi
Running: 65psi
It's just an autozone acctron or whatever fuel guage so it may be reading a little high. I also have the racetronixx hot wire kit on the car.
I looked at a few of the plugs they look a little sooty, and a few maybe a little wet (smelled like fuel and was the consistency of fuel). I do have a big overlap cam though, so it could just be fuel that fell into the cylinder when the car was shut off. They looked sootier then I thought they would be given that they're brand new plugs that have driven maybe 6 miles and idled for a total of 1-2 hours. The plugs ares stock gapped NGK TR6's, thats what the car has always had and was tuned for so I never changed brands/models.
Also, still no codes. Even when I unplugged one of the injector wires to connect a noid light (car still started and ran the same). Later tonight I think I'll noid light the rest but without the car running.
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Tech Contributor
Joined: Jan 2007
Posts: 19,350
Likes: 1,124
From: Dyer, IN
Whelp. I bought a timing light, all the plugs show good consistent rhythm so I guess its not the coils.
The fuel pressures were as follows:
Key to on, primed: 60psi
Cranking: 63-65psi
Running: 65psi
It's just an autozone acctron or whatever fuel guage so it may be reading a little high. I also have the racetronixx hot wire kit on the car.
I looked at a few of the plugs they look a little sooty, and a few maybe a little wet (smelled like fuel and was the consistency of fuel). I do have a big overlap cam though, so it could just be fuel that fell into the cylinder when the car was shut off. They looked sootier then I thought they would be given that they're brand new plugs that have driven maybe 6 miles and idled for a total of 1-2 hours. The plugs ares stock gapped NGK TR6's, thats what the car has always had and was tuned for so I never changed brands/models.
Also, still no codes. Even when I unplugged one of the injector wires to connect a noid light (car still started and ran the same). Later tonight I think I'll noid light the rest but without the car running.
The fuel pressures were as follows:
Key to on, primed: 60psi
Cranking: 63-65psi
Running: 65psi
It's just an autozone acctron or whatever fuel guage so it may be reading a little high. I also have the racetronixx hot wire kit on the car.
I looked at a few of the plugs they look a little sooty, and a few maybe a little wet (smelled like fuel and was the consistency of fuel). I do have a big overlap cam though, so it could just be fuel that fell into the cylinder when the car was shut off. They looked sootier then I thought they would be given that they're brand new plugs that have driven maybe 6 miles and idled for a total of 1-2 hours. The plugs ares stock gapped NGK TR6's, thats what the car has always had and was tuned for so I never changed brands/models.
Also, still no codes. Even when I unplugged one of the injector wires to connect a noid light (car still started and ran the same). Later tonight I think I'll noid light the rest but without the car running.
Thread Starter
Le Mans Master
Joined: Jan 2007
Posts: 9,844
Likes: 33
From: S. FLA :: Professional Devil's Advocate
If you have fuel fouled or sooty plugs, you may be chasing your tail. I'd throw some fresh plugs in there, before continuing. I'm also assuming that the valve train geometry is set up correctly, there is no bleed down when the fuel pump is primed, and you at least have a base tune for the new cam/heads.
The spark plugs are basically new. They've got 6 miles on them since I put them in. Valve train geometry is setup well and has worked when I first started the car (three tear downs ago).
The tune is good and is from a similar setup.
The fuel pressure bleeds down from 60 to about 55 psi within 2-3 minutes and down to 50 within 10-12 minutes. I'm not sure if that is a normal bleed down rate.
