DIY: Testing all RX-8 Coils and GM LS2/Yukon coils and sparkplug wires
 

Coils with internal ignitors can't really be checked effectively using resistance and continuity measurements as shown in the factory service manual. If you suspect a coil or wire is intermittently failing or misfiring the preferred method is to use an electronic ignition spark tester.

I bought this one from NAPA for about $14 locally; brand/part # OTC 6589

The HEI Spark Tester (The Best Spark Tester On the Market)


https://cimg0.ibsrv.net/gimg/www.rx8...979ae4349.jpeg
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(see attached image at bottom of this post)

It is essentially a special spark plug that requires the spark to jump about a 3/8" wide gap. The tester gap jump simulates a high load on the coil and wire. If either one is going bad it will almost always show up using this method.

Start the engine, bring it up to temperature, and then shut it down. Then take one plug wire off of a sparkplug and push the spark tester into the end just like a spark plug. The clip on the side of the tester is for securing it to a good grounding point. This is very important for the test to occur correctly. I used a set of battery jumper cables to ground the clip to the chassis. This allowed me to position the tester firing end where I could see it from the drivers seat with the hood up.

Once this is setup up you just crank up the engine. A good engine will fire and run with a missing plug wire regardless of position. When the engine starts a good coil and spark wire will result in a pulsing electrical spark across the tester end. Let it run for 15 or 20 seconds before shutting the engine down. Sometimes a failing coil will initially light off and then stop once the load generates internal heat within the coil body. So it needs to run a bit before shutting the engine off.

Repeat the process by replacing the sparkplug wire back on the appropriate plug and then move on to the next one until you have checked all four. If you have one or more fail you will then need to determine if it is the coil or the spark plug wire. You do this by removing the wire end from the coil, inserting the tester end into the coil output end so that the terminals touch, and then start the engine. The tester is a loose fit in the coil output end and this is where the battery cables also come in handy because the cable hand grip allows you to hold the tester in place within the coil without getting shocked after you start the engine. If the tester fires off the coil is good and the wire is bad, or possibly vice versa. Alternatively you can also swap in a proven good wire from another position and see what happens.

Repeat the tests to be sure. If the coil doesn't fire off without the wire then it may be bad, but also possibly the wiring or PCM has an issue. The simple way to test this is by swapping it with a good coil position and retest both. If the same coil still doesn't fire off you can be pretty sure that is the problem. If the previously good coil doesn't fire and the previously bad coil does fire after the position swap then you likely have a wiring or PCM issue, which is beyond the scope of this DIY.

I tried this tester with the OE Mazda coils and it worked perfectly. Found a bad OE coil that passed the service manual test, but otherwise was dead and not firing the sparkplug. The main difference between the OE coils and the LS2 coils is that the LS2 coils have a 4th ground wire that the 3-wire OE coils do not

Part 1 -How to Test the COP Coils (GM 4.8L, 5.3L, 6.0L, 8.1L)



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Where the hell was this a month ago :lol: Good write up.

Good explanation. It almost reads like an if/when chart. BHR should give you a nice discount for this, with the number of drivers using their setup.

NICE!!!!!!!!!!!!!!!! A lot easier than just randomly changing parts and hoping to find to bad unit.
Yes sir, Good Job!!!!!!!!!!!!!!!!!!!!!

Not really. Failures/issues are rare and I just pieced together some common GM info with my own experience

http://easyautodiagnostics.com/gm_co...oil_test_1.php

http://ls1tech.com/forums/3796925-post3.html

Etc. .... I actually saw the tester used to diagnose a misfire connection on a GM truck while flipping through the TV channels about a month ago ...

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Is there anything special about the plug? Couldn't I just take a cheap conventional plug, bend the gap open, and grip it with a jumper cable?

Used to do this kind of thing on piston engines in the old days by pulling a plug out and laying it on the block. Don't remember what I did so as to not get shocked. There's also the traditional method of grabbing the plug wires one at a time and seeing how high your elbow jumps for each. But that only works if you have a car where all the plugs are on top and easy to reach.

Ken

No. This is a special tool that is "similar" to a sparkplug, but designed to create a specific load on the ignition system that you cannot readily duplicate this way.

I've heard nothing but great things about BHR (I can't wait for the long tube header) I made the comment only as a compliment to Team, and I used the BHR name because you're the only manufacturers of a plug-in coil kit. This is espectially handy because of the of rarity of a failed coil, and I could see this coming in handy for such occasions. It can be frustrating to have an obscure issue and no insight. :dunno:

Respect to you both.
-JM

If anything it is just one way to rule them out from being related to a potential issue, but yeah, occasionally it happens :dunno:

So I managed to check out the spark tester tool linked in the first post above on the OE coils and it turns out this is probably the best way to check them. It indicated the factory T2 coil as being bad, but the coil passed the service manual test fine. It was completely dead and not firing the plug.

The only thing that is different in this tool than an over-gapped plug is the grounding clip.

I've been using this method to troubleshoot ignition systems for more than 25 years.

Why? Team didn't buy his ignition system from BHR.

It's quite different actually. They make a similar tool for "standard" ignition systems that is closer to what an over-gapped spark plug is than the HEI version in my link. One of the differences os that the center electrode protrudes out of the ceramic like a regular plug on the standard version while it is down inside the ceramic by over 1/2" on the HEI version. So it has to overcome this as well as the large gap from the ceramic to the outer shell. If you simply overgap a plug you really have no idea how much load you are creating relative to the tool i.e. you are guessing at the calibration. a dead coil will be caught by anything, but a weak coil, spark plug wire, or grounding point may or may not be caught by the guessing tool game. That's exactly why they tell you not to use a spark plug. It was cheap relative to avoiding one more source of error.

To hear you tell it, you invented the internet too .... lol. As for my kit, where I got it and what it is isn't relative to the DIY.

Uh, no.

V = 4.3 + 136 × (p / T) + 324 × (p / T) × Dg


V = voltage potential (kV)
p = absolute pressure in Bar
T = gas temperature (Kelvin)
Dg = electrode gap in mm

You can just use this calculator if you don't feel like doing the math:

Spark Gap Calculator

Surely not. But it was relevant to the suggestion that you receive some sort of compensation for "working out" some "solution" to an inferred "problem" with the BHR system.

I wish the stealership in Sarasota know how to do diagnostics like this they just charged me for 4 coils, plugs and cables. Good to know for future. I kept all the old coils so I might test them and sell the good ones.

I guess I wont be selling them then, I will keep them in a box in the garage with a load of other junk I will probably never use.

plenty of people got a lot more mileage than that from OE coils, most people change them without any idea if they are good or not, using the tool in post 1 will clear some of this up. That tool is made by numerous other suppliers, originally it was/is a GM factory tool

Thanks, Team - I will probably check mine in a week or two.

Good read ...
Thanks Team

Definitely a good write up. So far no issues here that could be coil related, but I will keep it in mind if something happens.

Good write up - subbed for future reference .

At least it's a procedure that definitely works. More than can be said about the Mazda service manual procedure, which is useless.

THE FACTORY SERVICE MANUAL PROCEDURE FOR TESTING OE COILS IS ABSOLUTELY USELESS!!!

I can't seem to get the word out on this

Not totally useless - It will show a completely dead coil, which is all Mazda cares about with regards to service/warranty.

My understanding is that a some of them (the smart ones) are using the testing tool or something similar to what I recommend. It's not unusal for a good factory technician to develop their own bag of tricks.

First, coming here from another thread, excellent tip!

Next, a couple of clarifications, based on a few decades of struggling the high-voltage devices. MM is correct in that calculating the voltage required for a given gap is rather straightforward. The voltage however says nothing about the power delivered in that spark. Charles is correct about this early-ish history of electronic ignition. The HEI (high energy ignition) is a true statement wrt classics points-condenser-coil ignitions or, god-help-us, magneto ignitions. However, too much power, eg. voltage x current in a spark is a really bad thing. The duration of the spark is also important. With the right (wrong) conditions the impact zone of a spark can raise the local temperature to levels that will vaporize anything. It can also destroy metals through a process called sputtering. Our HV power supplies are very robust (and expensive), but anything built to a cost, like auto ignitions, cannot be so robust, and also may be damaged by sparks of too much power. The solution? Properly sized resistors in the path from coil/power supply to the electrode (sparkplug). This will not change the sparkover voltage, but will limit the current (power) in the sparks.

thanks for your input, but that discussion of various posts is really beyond the scope of this DIY and really only serves to confuse the average enthusiast (that isn't your intent I'm sure, just the way I see it going).

I find the test tool works extremely well and is cheap enough to justify just buying one and keeping it for the rest of your car troubleshooting life. No moving parts and it never wears out.

Best $8 you will ever spend ;)

btw, several people sent me some OE coils to test and I haven't forgotten about them. My car has been up on jack stands for the last several months. Just had it running for the first time in forever the other night, without an exhaust manifold no less. Kind of cool to watch the flames lick out of the ports while idling at night with the lights out ... :)

Here is coil tester I used:

http://partimages.genpt.com/largeimages/255985.jpg

I took a quick video that shows what you should expect to see with properly working coil:

I have a buddy that has one of these:


Would this work like the tester in the OP as well? It seems this one still makes use of the spark plug so that you dont have to run the engine with 1 missing plug.

Nadrealista's video is aweome - Youtube has got automatic closed captioning now, and it's totally choking on this guy's accent:

"running in her parents protested for Wednesday ... regardless of oral sex constantly all-stars is due to the engine" etc.

bump, so easy to check, works on all RX8 coils OE or aftermarket

FYI, OTC makes a similar one for HEI system(model #6589), with the model #6588 being the standard. See attached photo to showcase the difference of electrode between the two. Standard on the left, HEI on the right (one needed for RX-8).

/\ That 'style' has been superseded for 'safety' for well over a year..

as long as you have a good ground and no metals near the tester, you should be safe. The only danger is the possibility of the current jumping to a stronger adjacent ground, but even that is a stretch.

Great Write Up. Subbed for Future Reference

Hey Team ... any chance you could find the tester you recommend again and post a pic ? The link just goes to Napa and I wasn't sure which tester you were referencing when I did a search of the site ......

This one

http://img1.fastenal.com/productimages/0245717.jpg

HEI spark tester

Yep. Picture is not accurate but this is the updated one.

Thanks guys :)

It was described and shown well in post #34

https://www.rx8club.com/series-i-do-...2/#post4462628



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Subbed

I just checked my coils with a tester made by OTC. Is it normal that when cranking, the trailing coils take 2 seconds before they start sparking? The leading coils spark right away. The test is being done with a cold engine because I just bought a 2004 with an engine that has low compression and won't start, compression test done by dealer from what I was told by seller. But I want to check everything before I decide the engine needs a rebuild. Thanks for answering

ok, just to also clarify for the next person who also searches this thread. This is a normal thing?

Somebody once claimed they didn't even spark during cranking. I know they do, but haven't done it in a while and am not sure/can't recall if there's a delay or not. Regardless, as long as they're actually sparking I can't see how even an initial delay would result in it having starting issues.

Thanks for the clarification!

bump for all the noobs - see post #1