Coil packs

Tiny
CHRISCHANDLER73
  • MEMBER
  • 2001 NISSAN SENTRA
  • 100,420 MILES
Is ther a way to check the coil packs with a digital multi-meter to see if they are good or bad?


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Wednesday, May 1st, 2013 AT 12:37 AM

3 Replies

Tiny
CARADIODOC
  • EXPERT
With no other details or information to go on, I would have to guess you're looking for the cause of a misfire. '96 and newer cars have the OBD2 emissions system which includes misfire monitors that detect which cylinder is misfiring. If you have the coil-on-plug ignition system, the easiest thing to do is swap the coils between that cylinder and any other one, then erase the fault code and see if a new code sets for that cylinder you moved the suspect coil to.

If you have the coil-on-plug or a coil pack you can measure the resistance of one and compare it to another one, but that is not conclusive. You will very rarely find a coil that is open, and even if some of the loops of wire are shorted together the lower resistance would still be within the acceptable range. Most coil failures involve internal arcing which won't be found with an ohm meter.

If you measure the resistance of a coil, either the primary or the secondary, and find it is open, then obviously you found the problem, but that is pretty uncommon. The service manual will give the resistance specs for reference, but if you find a coil that works fine, it is just as likely to be slightly out-of-specs as a failed coil that reads in-specs. So I guess to answer your question, yes you can measure them with an ohm meter, but no experienced professional would bother or waste their customer's time doing so. We don't like throwing random parts at a problem, but when the diagnosis leads us to an ignition coil, substitution is the fastest test.
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Wednesday, May 1st, 2013 AT 1:08 AM
Tiny
CHRISCHANDLER73
  • MEMBER
Ok, that answered that question. Now can you tell me if I checked my coils with my multi-meter correctly?

Here is how I did it, I set my multi-meter to: 2000ohms I then took each coil off of the car 1 by 1. I placed 1 lead on the negitive pin (coil) then I placed the other lead on the positive pin (coil). I was going for the "primary resistance" of the coil.

My meter showed nothing. No reading.

So I then moved the lead from the positive pin (coil) to the
high-tenison pin (coil) while leaving the other lead on the negitive pin (coil)
this was my attempt to get the "secondary resistance" of the coil

here were my readings: all 4 of the coils showed no reading when I was checking the "primary resistance" of each coil. But I got these readings for the "secondary resistance" of each coil.

Coil #1 - 1844
coil #2 - 1858
coil #3 - 1922
coil #4 - 1863
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Wednesday, May 1st, 2013 AT 1:43 AM
Tiny
CARADIODOC
  • EXPERT
First of all, can I assume you have the 1.8L engine with the coil-on-plug system? There are two different versions of the coils depending on the production date of the car. I've never tested one so I can only offer some suggestions.

Are you using a digital meter or an analog one with a pointer?

Normally the primary winding is between the two terminals in the connector and that reading is going to be very low, as in less than 2.0 ohms. Your meter leads will have more resistance than that so you can expect to find around, ... Oh, ... Perhaps 5 ohms. If you're on the 2,000 ohm scale that will read "0" ohms. You have to switch to the 20 ohm or 200 ohm scale to get the most accuracy.

Typically the secondary will read in the area of 12,000 to 15,000 ohms. On the 2,000 ohm scale of a digital meter that would read over range or open, ... The same as if the meter leads were not connected. Some meters go blank for that condition. Some read a single "1" on the left. The secondary connections are normally to the spark plug terminal and a metal insert on the mounting flange. The secondary has no connection to the two small terminals in the connector, but if you're finding something there, that might be some kind of radio noise suppression resistor they put in there. Since all four coils read the same I would have to assume that is normal, but 1.8k to 1.9k is too low to be the secondary coil. That wouldn't produce much spark voltage. Switch the meter to the 20,000 scale, (20k), then measure from the mounting ring to the spark plug terminal. I'll bet you get a much higher reading. You might even have to go to the 200k scale.
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Wednesday, May 1st, 2013 AT 3:14 AM

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