Can pulling the plug wires kill the coil? - Mazda MX6 Forums: MX6 Forum
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Old 4-8-12, 0:21   #1 (permalink)
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Join Date: Nov 2011
Location: , TX, USA
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Can pulling the plug wires kill the coil?

I probably have bigger problems than this….

Blew a coolant hose and now have combustion gas in the radiator! Overheats.

Anyway, V-6, 1994, 111k miles, runs great so I removed all the plugs for the first time ever to try to find out which cylinder had the blown gasket or head crack. Sprayed hemi holes with lube and let them sit for a few hours and got plugs out w/o incident. Because of the WD-40, plugs came out drenched in lube and couldn’t tell if any plugs were wet. Put plugs back and started engine. Pulled each plug wire and none were misfiring. Engine is still running fine and isn’t even warm yet.

Then I pulled the dipstick just to make sure there wasn’t water in the oil. There wasn’t.

Then the engine quits like someone turned off the key. No sputter. Just stopped. All wires were attached and motor was running great at the time.

Removed #2 plug and find no spark.

Could removing the plug wires, one at a time, like I did, fry the coil? It didn’t happen when I was pulling the plug wires; I had already finished and it happened a few seconds later. If so, what part did I fry? The ignition coil in the dist? Or something else? Checked all the fuses and they look okay.

How do you safely do a compression check, which was my next move?

Anyone interested in a slightly used 18 year old LS 5 speed with a blown head that ran great until it didn’t?

Any advice is appreciated.

Regards……Mark in Houston
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Old 4-9-12, 9:30   #2 (permalink)
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No it's not going to kill the coil. Take off the 1 single high tension wire from the coil and see if you get spark test from that 1 lead wire. If yes you know the issue is with the distributor. If no then probably the coil.

Removing and testing each wire/plug is the correct factory procedure for spark test. Your issue is not stemming from what you did there... unless you choose to use a sensor as the ground for the spark test... like a camshaft position sensor. That would be a stupid mistake but I'll assume you didn't do that.

The engine cranks over fine I assume?

Last edited by djdevon3; 4-9-12 at 9:33..

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Old 4-9-12, 11:36   #3 (permalink)
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Thanks......

Yes, it's cranking fine and making no attempt at starting, like, no spark and I see none when i pull and ground a plug. And no, I didn't ground to a sensor.http://www.mx6.com/forums/imagesmx6/smilies/smile.gif

All I did is lift each plug cap out of the valve cover an inch or two to check if each plug was firing. All were firing.

What's weird is, that's the only thing I did. These plugs and wires have probably never be touched since they left the factory. So the correlation of the spark failure with pulling the plug wires was my only conclusion. Like i said, weird coincidence?

You mention testing the main coil wire. Actually the coil is inside the distributor. The only lead goes from inside the distributor cap directly to the coil, which is under what i think is called the ignitor. There's a three wire plug to the coil. Anybody know what the Ohm reading should be on the three prongs to the coil?

And, how can i tell if it's the coil or the ignitor? And why would they fail, if they did, in a cold perfect-running motor in my driveway?

Thanks again.....I'm still stuck.
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Old 4-9-12, 14:42   #4 (permalink)
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Okay...More info:

Not sure of my multi-meter but, with the 3-prong connection to the coil unplugged, i get (on the coil side, of course) something less than 1 ohm between the 2 outside prongs and, about 1000 ohms each between the inside and each of the outside prongs

Anybody know if this means anything?

Thanks........
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Old 4-9-12, 16:07   #5 (permalink)
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Quote:
Originally Posted by mcypert View Post
You mention testing the main coil wire. Actually the coil is inside the distributor.
You're right sorry. I'm more used to dealing with ATX's. The MTX (FS & KL) has an ignitor module and the coils are in the distributor. The ATX has a separate ignition coil. My apologies.

Below 1.0 ohm is normal. It should be 0.58-0.86.

Suggest you read section G of the 1994 Manual.

Specifically page G-19 for testing the KL's primary & secondary coil windings. The FS MTX and KL MTX both use the same distributor.

Last edited by djdevon3; 4-9-12 at 16:26..

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Old 4-10-12, 0:16   #6 (permalink)
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Thanks devon:

That's a ton of info and I didn't know the manuals were out of print and available online. Obviously, I don't have and dearly need.

My mom's in the hospital so more urgent matters are pressing. I'll take a while to get back to this.

Finally, as I began this post, my coil/dist problem is minor compared to to my head leak. Over-heated my engine and now have combustion gas in the radiator. Haven't confirmed but looks like crack/ blow is in cylinder #2 (closest to passenger's side right corner of car if I'm counting my cylinders right). Anybody know of any correlation to overheat and much later coil/dist failure for no apparent reason? And, is it more likely the coil or the ignitor? Is the head closest to the radiator most likely to blow in an overheat? Perhaps someone else has been down this road?

Thanks to all......Mark in Houston

Last edited by mcypert; 4-10-12 at 0:18.. Reason: typo
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Old 4-12-12, 14:42   #7 (permalink)
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Get a compression & leak down test done. If you've blown a head gasket that would explain a lot of your symptoms except the no-start. That could still be a separate issue. Overheating will only cause premature distributor/ignitor failure on the MTX if driven in that condition over extended periods of time. Let's say 100-200 miles. It's the additional engine heat and cooling cycles that will help to fracture and break the coil but that's gonna happen over a period of time. It if started happening at the same time I'd say that's more than a coincidence and something else is causing both symptoms like bad timing coupled with a faulty engine coolant temp sensor.

It's hard to say. You need a lot of work done. Recommend it's time to see a mechanic.

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