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Discussion Starter #1
Just as the title says, How do you test an ignition coil using an ohm meter?

Im having an issue on my car ('01 ZX3 5 speed w/ the ZETEC motor) and I think it may be the coil, but my manual says I have to test the resistance for the primary windings and for the secondary windings[confused] does anyone here know how to do that?

I want to make sure I am testing the coil correctly before I decide whether or not to get a new one.

Any help would be greatly appreciated!!! Thanks!!!![:)]

(btw I already have the coil pack removed from the car)
 

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Discussion Starter #3
Ya, its misfiring/sputtering pretty bad. It also popped the CEL, I havent checked the code yet but im getting that done tommorrow (Im assuming its going to tell me its a misfire though).

So far I have checked the wires (all tested good) and plugs (they are new as of a couple months ago and they looked good as well).

I also checked the battery (wasnt that) and replaced the fuel filter (it was dirty and needed to be done anyways, but it didnt fix the problem)
 

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easiest way to check if your coil is trashed is to borrow a friends coil from thier car. it can be either a SPI or a zetec. if thier coil makes your car run better, yours is junk. this is the cheapest and easiest way. btw, its not hard to do either[thumb]

good luck
 

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easiest way to check if your coil is trashed is to borrow a friends coil from thier car. it can be either a SPI or a zetec. if thier coil makes your car run better, yours is junk. this is the cheapest and easiest way. btw, its not hard to do either[thumb]

good luck
I appreciate the suggestion but no one else I know has a Focus. That would be an ideal solution though lol.
 

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hold on.. lets first rule out vacuum leaks.. have a looksee at all your vacuum lines.. if your focus has a lot of miles on it.. they hoses probably would have perished.. some may be cracked thus allowing more air in and hence causing lean misfire.. or some could have collapsed inwards.. check the notorious PCV valve hose coming off the intake manifold.. and the lines that come out the back of the throttle body! once uve ruled out that.. then yea i think ur coil packs probably gone.. does the car shake at idle? like u can feel it shaking the whole chassis while ur sitting inside it??
 

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Ok, remove the plugs from the coil. Set your electrical tester to Ohms. Now start testing between the plug in prongs, between two of those you should get some sort of continuity and a reading in Ohms. Anything 0.xxx is too low, and is a failed reading. If you can't read any resistance then the coil is likely to be bad. That's the test on the primary side.

To test the secondary side find the positive terminal on the primary side, and put the other test lead in the coil output where the coil wire would connect. You should get some sort of reading in ohms around 15 or so- check your manual to be certain. A low resistance reading would be a failure, and no resistance reading would also be a failure. Most all failures will be no resistance- meaning the circuit can no longer be completed.

Check your service manual for more specific instructions and exact resistance readings.
 

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With a dual-fire coil, the secondary resistance would be measured between cylinders 1&4, and 2&3 (two measurements, take off the plug wires)
 

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Ok, remove the plugs from the coil. Set your electrical tester to Ohms. Now start testing between the plug in prongs, between two of those you should get some sort of continuity and a reading in Ohms. Anything 0.xxx is too low, and is a failed reading. If you can't read any resistance then the coil is likely to be bad. That's the test on the primary side.

To test the secondary side find the positive terminal on the primary side, and put the other test lead in the coil output where the coil wire would connect. You should get some sort of reading in ohms around 15 or so- check your manual to be certain. A low resistance reading would be a failure, and no resistance reading would also be a failure. Most all failures will be no resistance- meaning the circuit can no longer be completed.

Check your service manual for more specific instructions and exact resistance readings.
^^^ Also, some stores have a "coil tester" where we can run a coil on the bench just like its on the car. Nice device. We use ours all the time, but the resistance test as above will do the trick 99% of the time, good info there.
 

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Discussion Starter #10
Ok, remove the plugs from the coil. Set your electrical tester to Ohms. Now start testing between the plug in prongs, between two of those you should get some sort of continuity and a reading in Ohms. Anything 0.xxx is too low, and is a failed reading. If you can't read any resistance then the coil is likely to be bad. That's the test on the primary side.
When I test between the center prong (I belive this is the positive terminal) and either of the outside prongs I get a reading of 0.9 ohms. When I test the two outter prongs I get a reading of 1.4 ohms

To test the secondary side find the positive terminal on the primary side, and put the other test lead in the coil output where the coil wire would connect. You should get some sort of reading in ohms around 15 or so- check your manual to be certain. A low resistance reading would be a failure, and no resistance reading would also be a failure. Most all failures will be no resistance- meaning the circuit can no longer be completed.
For this I cannot get a reading, it keeps coming back as a infinite resistance no matter what prongs or coil wire connections I use

Check your service manual for more specific instructions and exact resistance readings.
I assume this means my coil is bad?[scratch]
 

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Discussion Starter #11
Oh, and thanks again for the responses!!!


Im going out now to check what code is popping my CEL, will be back in a few.
 

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Ok just pulled the codes

P0302 and P0303 - cylinder 2 and 3 misfire

P0352 - Ignition Coil B Primary circuit fault

Erased the codes and nothing came back right away, but the car doesnt really run well enough to be driven too far at the moment either.

Im probably going to try putting a coil in and hope thats my issue.
 

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It might be that you're not testing it correctly. If you have no resistance on a coil secondary- then that coil would not work at all. You wouldn't even get a misfire- no fire at all.

Did you try Emsvitil's suggestion? He may have written less than me, but I was going on general coil testing procedures. I don't own a Zetec, so I'm not as familiar with those engines and I forgot that those have coil packs when I was writing that.

From the ECU's description, I'd say you have a problem with coil B. Check the wiring plug FIRST!! Those have been reported to be the cause of many problems involving coils. If you can pull on the wires without pulling one out of the plug- then it's probably ok, and the coil itself is the problem. If you do pull one out, then you'll have to figure out some way to rig it up until you can get a new pigtail from a dealer.
 

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Discussion Starter #14
Well I found my problem.

Wasnt the coil, I thought that was it but apparently I was not testing it right. I followed the advice here to the best of my ability, but no luck on that one.

What it ended up being is exactly what whynotthinkwhynot said above, one of the wires for the plug that goes into the ignition coil correded to the point that it was barely connected. That wire pulled right out one of times I was taking the coil out of the car.

Got my new pigtail from the dealer this morning ($41) and put it in, problem solved, runs like a champ now lol. Hopefully this thread will be useful to others out there.........
 

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don't you just stick your tongue on it, and if it stings a bit, it still works? I know that's how you could check those 9V batteries. LOL please don't, if you're that stupid. (and I really don't think you are, though people do tend to amaze me sometimes, lol) [rofl]
 

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don't you just stick your tongue on it, and if it stings a bit, it still works? I know that's how you could check those 9V batteries. LOL please don't, if you're that stupid. (and I really don't think you are, though people do tend to amaze me sometimes, lol) [rofl]
ROFL. I was going to suggest. Hold tongue to coil output. crank car. If it hurts a bit. Coil is bad. If you fly across the garage, coil is OK. If you catch fire while flying across the garage. Coil is excellent! [eek]

Glad you found it!
 

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^^^ Thats a good description right there ^^^. ROFL.
 

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Problem With Coil Pigtail Lead Wires

If the problem is the pigtail wires leading to the coil primary side; would the misfire be in multiple cylinders?

If there is a misfire in only one cylinder, and the spark plugs are new; does that mean a P030x engine code (misfire) is more likely a spark plug wire than the coil?
 

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Pigtail wiring, if it doesn't shut it down entirely due to power loss at the center terminal, would lead to pairs not working for a total failure of one of the ground leads or a random failure in a pair when it's an intermittent.

On the output side a partial failure often results in a single cylinder getting a weaker spark. That's the most common coil issue seen with these.

Input & output are both paired 1-4 & 2-3.

High tension wire issues also usually affect one cyl. the most. If wires are long enough, they can be swapped between cylinders to see if the problem follows. Remember to swap the same at each end of course.
 
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