e36 - How to test coil packs (w/ pics)

[Auto Parts Guy]

I just wanted to post up some pictures on testing coil packs. This was done on my 1993 BMW 325i but it's similar on others.
ENJOY!!

Here's some instructions from the handy dandy Bentley Manual for the I-6.



Remove the plastic cover to expose coil packs. To unplug them just lift up on the metal clip and the plug pulls right out.
The coil packs are held in by (2) 10mm bolts each with the ground wire connecting them all as well as a ground strap to the head.
Remove those two "I" shaped clips that you see on the plastic cover in the next pic and move the wires out of the way.




Here you can see the top of the spark plugs on some and the coil packs ready to come out on the others.
Once unbolted and unplugged, the coil packs will lift right out. I had to use a little force to get mine out but they just pull straight out.


Coils out, now I'm ready to change my spark plugs.




Here is a cheap digital multi-meter (DMM) that I got from Harbor Freight for $1.99. I have like 3 of em; they do just fine.

You want to set your DMM to the lowest setting in ohms (which is not shown in this photo) in order to measure the resistance.
The reading should be between 0.4 - 0.8 ohms across the two end terminals (green arrows), per the Bentley Manual.




Touch one lead either (+) or (-) to the left terminal and the other lead to the right terminal.
Mine read 0.8 ohms on all my coil packs so Ima throw them back in there since I have had no problems out of them.




This isn't necessary but I vacuumed around the spark plug holes so
nothing would fall into the combustion chamber when the spark plugs were removed.




For all those hard to reach places




New NGK BKR6EK (2288) spark plugs going in. I was glad to see the PO also used these plugs.

[EThirtySicks]

Pretty straightforward, but thanks for making it that much easier with pics.



Good work!

[jmo69]

Very helpful and informative. You can tell from the plugs that your coils are good. Nice light brown center porcelain. I'm assuming that you could check the resistance w/o removing the coil from the plug.

[Auto Parts Guy]

Very helpful and informative. You can tell from the plugs that your coils are good. Nice light brown center porcelain. I'm assuming that you could check the resistance w/o removing the coil from the plug.

Yeah you could just unplug it and measure it, instead of taking them out but I was changing the spark plugs anyway. It's very straightforward I just snapped some pictures while I was doin it.

[fun2drive]

That is a nice write up for the primary coil. Problem is most fail at the 2ndary coil which you can't measure and you need to have a good diagnostic tool real time to do so.

This works well on the primary however if you are that lucky vs 2ndary.
Nice pics...

[casper23]

Should the readings be the same with the coils on a 318? I haven't yet been able to test mine yet but it would be nice to know what i should be looking at.

[Compactive]

another tricky thing is guys, your coil pack may read perfectly but not fire due to any hairline cracks like mine has here

[maverick831]

dont know if this thread is still alive but i just did the same test with the same equipment my readings were 1.7/2.3/2.3/2.0/2.2/2.2 are my coils good or bad.only different i have a e39

[NicholasPostema]

I just tested my coils. I have an even .3 on all.

However, I don't know if this is acceptable. The diagram at the top shows .4 to .8

My vehicle will not start. I do not know if this will help you or not but it's all I have at the moment.

[RNeil]

You need special equipment to measure resistance less than one ohm. Multimeters will display a number, but it is not reliable, not even Fluke. You need something like:
http://www.biddlemegger.com/cgi-bin/...onfig=ent-dlro

[mgoods50]

OMG. I came across this thread after surfing along looking at plug wear pics.

A $6K - $7K piece of equipment was suggested to measure low ohm resistance on the coilpacks- and you can buy what you NEED to test them right for half that.

BTW, my snap on measures low ohm; it was about $300.

An oscilloscope, which is what you need to test coils, is roughly a couple thousand. THE reason it's cheaper to buy new coils and be done. I'd have to replace coils 10 times before I got near the price of the equipment.

[Beitie]

When I was in school, we used some nice Oscilloscopes to look at spark in cylinders, however they required a distributor cap, and a single coil system. Are there new scopes that do the DIS systems that we currently run? I wouldn't buy one myself, but I'm always interested in new technology.

You're right though, no logic in the world would allow you to buy a $6-$7K product to measure resistance on something that costs $20 to replace. Especially when that resistance measured is not even the most important thing to measure in this situation.

[Tonkabot]

You need special equipment to measure resistance less than one ohm. Multimeters will display a number, but it is not reliable, not even Fluke. You need something like:
http://www.biddlemegger.com/cgi-bin/...onfig=ent-dlro

That is not true, using a good meter with leads clamped on can measure low resistances just fine. Using a 4 wire meter like my desktop fluke would also measure just fine without need to zero the probe resistance out which using my handheld Fluke would require.
The problem, as another poster pointed out, is that it is the secondary coil that goes bad more often than the primary. I believe there is a spark gap internal to the device which makes directly measuring the secondary resistance impossible.
To add to the problem, sometimes the coils only go flakey after they have heated up. I suspect those ones with cracks can be flakey that way.

[cabdolla]

Nice attempt, however, not very useful. A digital multimeter does not have the resolution to measure the circuit. The measurement erorr in the multimeter is orders of magnitude larger than what you're trying to measure.

[hide1]

Well timed resurrection bump there. I was just wondering how to test them reliably. .

[Elementd]

I did this today and I got a 1.0 resistance across the board with my coils and about 26 across the board when testing the plugs. I have massive shuttering. They all get the same amount of and nothing is fluctuating. Help?

[hide1]

I did this today and I got a 1.0 resistance across the board with my coils and about 26 across the board when testing the plugs. I have massive shuttering. They all get the same amount of and nothing is fluctuating. Help?

You have vacuum leak, bad ignition coil boots, or bad ignition coils. You can't accurately measure the coils so don't bother. Rule out the first two and replace coils if problem persists.

- - - Updated - - -

another tricky thing is guys, your coil pack may read perfectly but not fire due to any hairline cracks like mine has here

My coils looked the same.

[B234R]

I´ve just tested my coils, multimeter gave a 0.9 ohms in every coil. It seems out of the 0.4-0.8 range, but I suppose the reliability of a $15 multimeter is relative...
Is 0.9 any good?

Every coil boot is broken like this, although a mechanic told me that "didn´t matter".

20170323_190221 (Large).jpg

[Eric93se]

Yes, 0,9 ohms is good, but that only means the primary coil is good. There are lots of other failure modes for the coils, the high voltage can leak out and short to ground and you won't get a spark at all, or do it intermittently. It can also short internally. The test provided by the manual is very rudimentary. If your coils are original then it's a good idea to replace them. I see your in Spain, I don't know how good ebay or other parts sources are but here in the US we can get a brand new set of coils for around $60 shipped.

I´ve just tested my coils, multimeter gave a 0.9 ohms in every coil. It seems out of the 0.4-0.8 range, but I suppose the reliability of a $15 multimeter is relative...
Is 0.9 any good?

Every coil boot is broken like this, although a mechanic told me that "didn´t matter".

20170323_190221 (Large).jpg

[BeanDip]

Mine tested 1.0 all the way across with some cheap multimeter, they're from a 92

Sent from my Nexus 6P using Tapatalk

[Eric93se]

Here are a set of coils on aliexpress:
https://www.aliexpress.com/item/CARB...815855573.html


Here is ebay spain:
http://www.ebay.es/itm/6X-FOR-BMW-5-...-/252238856360

[bluptgm3]

while this may be the case it is generally a sign that the rubber boot is breaking down and is or will be "leaking".

[BeanDip]

I swapped an s50 into my 92 E36 the motor didn't come with coilpacks so I used the ones from my m50nv, when I tested them with the multimeter they all measured 1.0 should I replace them? Do y'all think that .2 difference will make a difference on how the motor runs? I feel it runs fine.

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[B234R]

Yes, 0,9 ohms is good, but that only means the primary coil is good. There are lots of other failure modes for the coils, the high voltage can leak out and short to ground and you won't get a spark at all, or do it intermittently. It can also short internally. The test provided by the manual is very rudimentary. If your coils are original then it's a good idea to replace them. I see your in Spain, I don't know how good ebay or other parts sources are but here in the US we can get a brand new set of coils for around $60 shipped.

So the resistance measure test isn´t very reliable...
The coils are original, a set of new ones surely won´t do any harm. Thanks for your ebay links, although I found a shop that will sell me a set of new NGKs coils and boots for a bit under $200. By the way, is any coil brand to prefer? NGK, Bosch, Bremi...

I´m not happy with my car, it goes well and passed emission tests a couple of months ago, but I don´t think the engine is very smooth. It´s my first BMW and always believed they were super smooth and sounded great (even M52s, people say M50s sound better)., but mine ... I´m thinking in installing INPA in my old laptop and find out...

Thanks!!

[Eric93se]

Take a look at what your supplier has and compare the shape of the bottom of the coil, if its round then it's what most aftermarket sellers have (and ~110EU on spain ebay), if the base is trapezoidal like the pictures in the first post then they are original OEM. Which is better, well no one has done any real world testing, BUT BMW plastics from the 1990's was junk so there is a chance that newer designs are better.