Coil primary and secondary resistance??
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Joined: Nov 2006
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Here you go (been there done that)
Originally Posted by SVTRobG
Rob,
You can check the resistence on the coils to see if any are bad.
Specs are...
Primary resistence = 0.55 ohms
Secondary resistence = 5.5 K-ohms
You check the primary by connecting your ohmmeter to the + & - terminals of the coil pack.
You check the secondary by connecting the ohmeter to the + on the terminal and the - on the spark plug side (there's a coil wire inside the boot).
If the coil pack doesn't test out to those specs it's crap !!!
You can check the resistence on the coils to see if any are bad.
Specs are...
Primary resistence = 0.55 ohms
Secondary resistence = 5.5 K-ohms
You check the primary by connecting your ohmmeter to the + & - terminals of the coil pack.
You check the secondary by connecting the ohmeter to the + on the terminal and the - on the spark plug side (there's a coil wire inside the boot).
If the coil pack doesn't test out to those specs it's crap !!!
Junior Member
Joined: Aug 2007
Posts: 12
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From: Jacksonville, FL
Originally Posted by 02Bolt
Thanks Rob. Iv'e been searching all over for that. I thought it was just posted a couple of days ago. Maybe I over looked it.
Shef
Shef
Primary side on 4 of 4 COPs = 0.1 ohms
Secondary on 3 of 4 COPs = 6.2K ohms
Secondary on 1 of 4 = 5.6k ohms
I'm thinking it's the one that's reading at 5.6k, since the rest all match up with nearly the same resistance, but everything I've read says what u guys are saying... 0.55 for prim, and 5.5k for sec... what's up??
Junior Member
Joined: Aug 2007
Posts: 12
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From: Jacksonville, FL
Re-tested COP resistance. Input needed.
Originally Posted by Bird
It looks like you may have an ohmeter that is slightly out of callibration and 1 coil with shorted secondaries.
Bird
Bird
Retested 7 of them, with better results.
6 out of 7 = 5.4K ohms (slight variations, between 5.39k to 5.45k)
1 out of 7 = 4.2K ohms
The one with less resistance seems to be a different brand and newer, since I had a plug blow out nearly a year ago, and the mechanic I took it took replaced the COP that was destroyed.
My question is this: would resistance so far out of spec indicate a problem, or perhaps they installed a "performance" COP? Not sure how the resistance effects the current produced, and whether replacing it would make any difference. It's my understanding a non-working COP would read infinite resistance. Is this accurate?
Thanks in advance for your responses.
Technical Article Contributor
Joined: Oct 2005
Posts: 25,641
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From: MI
COP's can pass Primary and Secondary testing all day long and still be bad (been their done that). Easy solution is just to replace all when problems begin.- Low grade miss fires are a PITA. If your running stock units, only costs $85 for a complete set - Cost effective for COP issues.
Last edited by jbrew; Jan 12, 2008 at 11:22 AM.
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Junior Member
Joined: Aug 2007
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From: Jacksonville, FL
Originally Posted by jbrew
COP's can pass Primary and Secondary testing all day long and still be bad (been their done that). Easy solution is just to replace all when problems begin.- Low grade miss fires are a PITA. If your running stock units, only costs $85 for a complete set - Cost effective for COP issues.
Most parts stores around here list them for $50-70 a piece!
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Joined: Oct 2005
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From: MI
Technical Article Contributor
Joined: Oct 2005
Posts: 25,641
Likes: 19
From: MI
If your have a low grade misfire issues you can kick start the monitor . The Misfire monitor can pick up a hard to detect misfire that isn't producing a MIL.
Drive Cycle - Speed up under normal acceleration to 60 mph. Take you foot of the gas and DON'T touch the brakes until you decel to 40 mph.
Do this twice within the same drive cycle. It doesn't have to be consecutive ,but needs to done twice to start the monitor.
With the monitor active , find the rpm range where the engine mis-fires and hold it there.
Watch for a blinking light thus revealing the cylinder # fault when scanned. Code is set after the blinking sequence.
Drive Cycle - Speed up under normal acceleration to 60 mph. Take you foot of the gas and DON'T touch the brakes until you decel to 40 mph.
Do this twice within the same drive cycle. It doesn't have to be consecutive ,but needs to done twice to start the monitor.
With the monitor active , find the rpm range where the engine mis-fires and hold it there.
Watch for a blinking light thus revealing the cylinder # fault when scanned. Code is set after the blinking sequence.
Junior Member
Joined: Aug 2007
Posts: 12
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From: Jacksonville, FL
Originally Posted by jbrew
If your have a low grade misfire issues you can kick start the monitor . The Misfire monitor can pick up a hard to detect misfire that isn't producing a MIL.
Drive Cycle - Speed up under normal acceleration to 60 mph. Take you foot of the gas and DON'T touch the brakes until you decel to 40 mph.
Do this twice within the same drive cycle. It doesn't have to be consecutive ,but needs to done twice to start the monitor.
With the monitor active , find the rpm range where the engine mis-fires and hold it there.
Watch for a blinking light thus revealing the cylinder # fault when scanned. Code is set after the blinking sequence.
Drive Cycle - Speed up under normal acceleration to 60 mph. Take you foot of the gas and DON'T touch the brakes until you decel to 40 mph.
Do this twice within the same drive cycle. It doesn't have to be consecutive ,but needs to done twice to start the monitor.
With the monitor active , find the rpm range where the engine mis-fires and hold it there.
Watch for a blinking light thus revealing the cylinder # fault when scanned. Code is set after the blinking sequence.
You said it will reveal the cylinder # fault when scanned... I assume this means I need a good code scanner for this to work.
It idles very poorly, I have a lack of power, shakes badly under load, and occassionally acts as if I'm running out of gas at highway speeds.
I've replaced all the plugs, but the COPs are mostly original, and I've got over 100k miles on the truck. I haven't checked the O2 sensors or cleaned the MAF yet. I tried using a friend's scanner, but no CEL was showing, and no codes. Not sure if my custom SCT tune is bypassing the CEL from showing up... which might be the case.
I'll try your suggestion, though. Thank you.
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Joined: Oct 2005
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From: MI
The options get more expensive and time consuming if the drive cycle mis-fire monitor fails to reveal the faulty coil. That's just a part of the reason why I suggest replacing all COP's with high mileage .
A favorite low grade misfire point is @ 45 -50 mph usually following the shift into OD under normal acceleration.
Stress testing at the dealership is another option (Mode 6 cylinder history) - It's pricey.
Stress testing under load can be done by the DIY'er . This involves a COP probe clamped to the side of one of the eight. Lengthen the probe light wires through the firewall to monitor your converted low voltage to pulse signals generated threw the COP windings. During the drive cycle of course.
COP windings break down with age and become weak. The cost of a fresh set today makes said testing just about obsolete.
Do yourself a favor and purchase a new set. That way you the problem is solved promptly, cheaply and this also keeps ignition integrity in full swing.
It's the best tune up for a COPed motor with the mileage yours has IMO.
BTW - Auto Zone and a few other 3rd party auto suppliers offer free scanning. You DON'T need the Malfunction Indicator Lamp (MIL) illuminated to have a fault code stored. Blinking check engine light = code pending then stored.
Make sure you look at the scanner numbers yourself for a 300 series code.
A favorite low grade misfire point is @ 45 -50 mph usually following the shift into OD under normal acceleration.
Stress testing at the dealership is another option (Mode 6 cylinder history) - It's pricey.
Stress testing under load can be done by the DIY'er . This involves a COP probe clamped to the side of one of the eight. Lengthen the probe light wires through the firewall to monitor your converted low voltage to pulse signals generated threw the COP windings. During the drive cycle of course.
COP windings break down with age and become weak. The cost of a fresh set today makes said testing just about obsolete.
Do yourself a favor and purchase a new set. That way you the problem is solved promptly, cheaply and this also keeps ignition integrity in full swing.
It's the best tune up for a COPed motor with the mileage yours has IMO.
BTW - Auto Zone and a few other 3rd party auto suppliers offer free scanning. You DON'T need the Malfunction Indicator Lamp (MIL) illuminated to have a fault code stored. Blinking check engine light = code pending then stored.
Make sure you look at the scanner numbers yourself for a 300 series code.
Last edited by jbrew; Jan 13, 2008 at 07:03 PM.
Junior Member
Joined: Aug 2007
Posts: 12
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From: Jacksonville, FL
Originally Posted by jbrew
The options get more expensive and time consuming if the drive cycle mis-fire monitor fails to reveal the faulty coil. That's just a part of the reason why I suggest replacing all COP's with high mileage .
A favorite low grade misfire point is @ 45 -50 mph usually following the shift into OD under normal acceleration.
Stress testing at the dealership is another option (Mode 6 cylinder history) - It's pricey.
Stress testing under load can be done by the DIY'er . This involves a COP probe clamped to the side of one of the eight. Lengthen the probe light wires through the firewall to monitor your converted low voltage to pulse signals generated threw the COP windings. During the drive cycle of course.
COP windings break down with age and become weak. The cost of a fresh set today makes said testing just about obsolete.
Do yourself a favor and purchase a new set. That way you the problem is solved promptly, cheaply and this also keeps ignition integrity in full swing.
It's the best tune up for a COPed motor with the mileage yours has IMO.
BTW - Auto Zone and a few other 3rd party auto suppliers offer free scanning. You DON'T need the Malfunction Indicator Lamp (MIL) illuminated to have a fault code stored. Blinking check engine light = code pending then stored.
Make sure you look at the scanner numbers yourself for a 300 series code.
A favorite low grade misfire point is @ 45 -50 mph usually following the shift into OD under normal acceleration.
Stress testing at the dealership is another option (Mode 6 cylinder history) - It's pricey.
Stress testing under load can be done by the DIY'er . This involves a COP probe clamped to the side of one of the eight. Lengthen the probe light wires through the firewall to monitor your converted low voltage to pulse signals generated threw the COP windings. During the drive cycle of course.
COP windings break down with age and become weak. The cost of a fresh set today makes said testing just about obsolete.
Do yourself a favor and purchase a new set. That way you the problem is solved promptly, cheaply and this also keeps ignition integrity in full swing.
It's the best tune up for a COPed motor with the mileage yours has IMO.
BTW - Auto Zone and a few other 3rd party auto suppliers offer free scanning. You DON'T need the Malfunction Indicator Lamp (MIL) illuminated to have a fault code stored. Blinking check engine light = code pending then stored.
Make sure you look at the scanner numbers yourself for a 300 series code.
It's running much better now, I can tell the difference. It has more power, doesn't shake as badly. It's still a little rough under load, around 1-1.5k rpms, or 40-45mph, and I think I've got an exhaust leak on the passenger side manifold I need to fix, but it's at least tolerable to drive to work, until I get the money to take it somewhere.
Thanks again for everyone's response, especially jbrew.
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Joined: Oct 2005
Posts: 25,641
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From: MI
Originally Posted by jhand
Once I get paid, I'm going to replace the whole set like you suggested. In the meantime, I was able to swap out the faulty COP with a new one, and return the faulty one to the place I bought it, so basically did a free repair... tight.
It's running much better now, I can tell the difference. It has more power, doesn't shake as badly. It's still a little rough under load, around 1-1.5k rpms, or 40-45mph, and I think I've got an exhaust leak on the passenger side manifold I need to fix, but it's at least tolerable to drive to work, until I get the money to take it somewhere.
Thanks again for everyone's response, especially jbrew.
It's running much better now, I can tell the difference. It has more power, doesn't shake as badly. It's still a little rough under load, around 1-1.5k rpms, or 40-45mph, and I think I've got an exhaust leak on the passenger side manifold I need to fix, but it's at least tolerable to drive to work, until I get the money to take it somewhere.
Thanks again for everyone's response, especially jbrew.