Dizzy rotor button melt down question
 

Has anybody seen this before? I discovered it when I was transplanting the dizzy from my old reliable White One, which had recently lost power, into the Silver One, who's dizzy was not making me happy. When I took the distributor cap off some stuff came out and I discovered this:

http://i259.photobucket.com/albums/h...n/DSCF1291.jpg

http://i259.photobucket.com/albums/h...n/DSCF1293.jpg

http://i259.photobucket.com/albums/h...n/DSCF1294.jpg

http://i259.photobucket.com/albums/h...n/DSCF1296.jpg

http://i259.photobucket.com/albums/h...n/DSCF1297.jpg

Cap looks normal

http://i259.photobucket.com/albums/h...n/DSCF1298.jpg

Any body seen this? Looks like Old School to me.

Looks HOT lol...


Ive honestly had lots of weird problems with dizzy caps/rotors. From busted rotor "legs" to melted sections like you experienced. The weird thing is it seems like hit and miss. At least for me. I make sure everything is good (mounted properly) and sometimes they last a good amount of time and other times it will blow itself up in less than 100 miles or just suddenly shit out after 5000 miles.

That one had been in there for at least the last 30,000 miles. Just blew up one day on my way into work.

well um....at 30,000 miles i will say its time for it to be laid to rest lol. I change cap and rotor once a year on all my vehicles that need it plugs too.

man that looks like it got hot alright. I have yet seen one do that.

mustve had resistance or build up or wear perhaps on the inner ground flat connections and since electricity is lazy it goes the shortest route to discharge probably on the dizzy rotor stem ground which caused high heat which melted your distributor rotor.

ive had cracks on the "legs" as well and now i just discovered the base of my new one i just bought today is cracked around the ground pins. why cant all mazda dealers stock up on our old parts? i had to drive to my third furthest mazda dealer just to pick up a rotor

Yeah but Ben, what made it do that? That was a perfectly functioning rotor button when it quit.

There was some kind of evil event that came down and struck the White One last Monday. A brand new rotor button would have done that under the circumstances. It's like something possessed the White One that day and blew out her rotor button.

Lightning strike? (just kidding)

If one of the internal brass or copper conductors (which connect the top-center rotor contact to the lower arms) cracked inside the rotor body, electricity would be arcing across the gap with every plug firing.

Arcs create high heat (otherwise spark plugs wouldn't work), which will both widen the gap, and also melt the plastic. Keeps getting hotter and wider until it reaches the point that it's too wide to carry the arc.

It also would have made things quite warm inside the the cap. I can't see the button too clearly in the picture, but it could have overheated or started binding to the top of the rotor (due to molten plastic inside the dizzy flying all around) which would wear it down/melt it pretty fast. Or it might have been off-center, dramatically increasing friction on the button.

It certainly looks like a lightning strike!

DD the damage seems to be limited to the rotor button, neither the cap or the dizzy itself show any evidence of damage, including the carbon contact at the top of the cap. A lot of heat or electrical arching would seem to be the cause, but I can't figure out why that happened, there was no evidence of overheating in the engine (I have both the stock electrical and an add on mechanical temp gauges working at the time it happened, all was normal).

What I am most curious about is whether this had anything to do with the loss of power and compression in the rear rotor that happened while I was traveling out on the highway. I can't figure out a way to connect the two and I can't really be sure they happened at the same time but it sure is suspicious.

Both the loss of compression that sidelined the White One and that damage to the rotor button would seem to be fatal, so I don't see how they can be separated but I guess I could test that by installing the rotor into a functioning engine.

When all that arcing occurred it could have fired a plug at just the wrong
time and possibly cause a severe misfire that then took out one of the
old seals on the rear rotor.

Ray did you lose all compression on the rear rotor or just two faces?

That remonds me I better replace my cap/rotor soon.

My mistake; when you said "button" I was thinking of the carbon button in the top of the cap. What you call the button I just call the rotor. Terminal error on my part.

The top contact and lower arms on the rotor; are they for the leading or trailing circuit? (I don't have any way to check ATM)

I did a ghetto compression test, here's the videos. Basically I couldn't hear any swoosh on the back rotor, which was consistent with the gross loss of power, so I just figured it was toast. But I'm getting more curious now, I think I'll put a compression tester on that rear rotor to answer your question Tim.

DD I believe the top arms are trailing and lower are leading, however at the time I had my 2GDFI hooked up so the leading were direct fire, bypassing the dizzy and the trailing wires were moved to the leading ports on the dizzy, which would be the lower ones on the rotor button arms.

Symptoms:

http://i259.photobucket.com/albums/h...en/th_A-19.jpg

Plugs show lean burn:

http://i259.photobucket.com/albums/h...green/B-14.jpg

Front and rear rotor compression "tests"

http://i259.photobucket.com/albums/h...reen/th_b1.jpg

http://i259.photobucket.com/albums/h...en/th_C-11.jpg

Ray if you can just turn it slowly by hand it might be a lot easier to tell.

Ray outside of the deposits on the plugs they look optimal to me.

OEM cap and rotor? stuff like this is pretty common on other mazda's...

Thanks for the tip Tim, I'll give that a try when I get home.

You are right Ben, those plugs were getting a few miles on them, I thought the white deposits indicated it was a bit lean and I had recently adjusted the mixture, but maybe that's just a coincidence.

I'm not sure but I doubt the cap and rotor are OEM, I'll check to see if the terminals on the cap are copper like the OEM ones.

This is getting interesting.

you're never gonna get a good plug read unless you kill the car at idle mid or wot to determine. DOnt believe the myths though porcelain does not always tell the tale of jetting but the base ring does. your base ring is only 1/3d black it should be 270 for optimal jetting depends how you run the motor. when i pull wot in my z bare in minds i runs 6's so they are hot. The porcelain is so hot it stays white. but the afr and base ring says 13.8

Do your car a favor change plugs and cap rotor annually cheap insurance.

Ray

I think that whenever you are looking at heat buildup in the ignition system, it usually comes down to grounding. Whether the issue is the plugs (fouled, or otherwise not flowing the juice correctly), or engine grounding (probably the most likely suspect), or bad cables, it should theoretically give the same results.

yup fire it up and night and look for the light show

Okay, so the normally-leading contacts on the dizzy were being used for trailing... I'd bet a cookie looking at that damage that you were only firing trailing at best every other firing event, and it quite possibly could have been munging up the timing of that firing, too.

Normally, loss of trailing isn't terminal... but firing off-cycle or intermittently might produce a perceived drop in power under load. Bad enough, it would maybe feel like a misfire.

I hope it turns out your old engie is actually fine - - even though it'd be quite a pisser to have put all this time into an unnecessary swap.

i have run trailing of leading side when using direct fire for years without a issue.

I just watched the video ray. It sounds like nothing on the back. sounds like either 2 apex or a side seal bit the dust. that one has got a butt load of miles does it not?

Its weird though every time i have popped a rotor the engine looks like its gonna jump out and run away.

I'm sure, I'm just saying that as this was failing, it probably acted fairly squirrelly on the way out, rather than just failing completely like a switch was cut off.

My car has part-time trailing ignition (part of the smog setup; ) I can hear, and to a small degree feel, when it is operating and when it is not. Subtle but noticeable change in engine sound.

I wonder if firing trailing sufficiently out-of-phase could lead to seal failure? Just theorizing.

it can fire the rotor backwards if it happens before leading and if its to far behind it can fire right into a seal. But i dont think the pot can be adjusted far enough for the later but it can fire before the leading causing a kick back.

Thanks for the feedback guys, this is very helpful. Ben after seeing that test on the back rotor I was pretty convinced it was toast, the front one swoooshes a nice even three beat, but the back one doesn't swoosh at all. In fact I was so convinced I didn't even bother with the compression test.

But now that I've discovered this issue with the dizzy I'm wondering if there might of been a connection. Maybe a miracle will happen and it will turn out that the engine in the White One is fine, just an ignition problem. That explanation sure would fit the symptoms better, the car was running fine and strong, absolutely no indication anything was wrong until all of a sudden it lost power out on the freeway at 80 mph. When it happened I was pretty sure it was in the ignition because it was so sudden, probably the leading igniter, but turns out that was OK. But now I'm wondering what that mess in the dizzy might have had to do with it...

I'm going to throw a battery back in the white one and have a closer look at that back rotor (or just use Tim's method and crank it by hand and feel/listen for the swooosh). I want to be real sure that rear rotor is bad before we tear into it. This wouldn't be the first time the 12A in the White One has been declared dead prematurely.

And if it is still good, well that's a problem I wouldn't mind having. Sure I've invested a lot of time swapping everything to the Silver Car, but I don't mind, it's been fun, the White One can use a rest and the Silver One can get a workout.

ray check pm

Kind of on the same subject, but how often are you supposed to change the cap and rotor?

i dunno i did it yearly but prob every 10,000 miles

Oh, oops... I change mine with every oil change. Although I only change my oil once a year.

I've always just waited until they start to show wear on the terminals, thinking that's all that matters. Is it possible that the plastic and internal contacts deteriorate too?

In this case both the rotor and cap had some miles on them, but other than the blow out in the rotor, they still look pretty good (see the pictures above). Only average wear on the terminals, no pits, grooves or excessive corrosion. The cap has the copper terminals (or is it brass), which makes me think it's one of my OEM ones.

I don't think this rotor button blowout was caused by a faulty cap or rotor, something weird happened and it was probably related somehow to the loss of compression in the rear rotor.

Incidentally, as Ben and I suspected, that rear rotor really is toast, I just went out and checked it more carefully, it's got nothing coming out of the spark plug holes and the T2 hole seems to be messed up, I can only screw the plug back in half way before meeting some resistance.

In any case, I won't be putting that dizzy back in anything soon, until I figured what the connection between the rotor button blow out and the rear rotor blow out is.

Quite possible that whatever caused the compression loss (side seal, maybe?) also dead-shorted the plug, which could cause overcurrent conditions in the trailing circuit, which in turn heated and melted the dizzy button.

Shorting the plug is like removing most of the resistance off the circuit, and with electricals, as resistance drops, current rises in proportion - - it's like unclutching a motor at full load. Very much the scenario Kentetsu was talking about.

i am gonna go with the grounded plug at high load too. ray i think somehow the seal apex or side slammed into the trailing hole as small as it is i guess it could happen. Grounded an overloaded the lead and it had to go somewhere.

When you take that motor apart its gonna be interesting to see what is embedded in that tiny as pin hole they call trailing lol.

Now that I can see the photos, I still think that's what it is. The spark found an easier path to take, which seems to have involved the shaft of the distributor. I wonder if it might have cracked on installation, making it even easier. So, once the plugs were more effort than the dizzy shaft, things started getting hot.

"Quite possible that whatever caused the compression loss (side seal, maybe?) also dead-shorted the plug, which could cause overcurrent conditions in the trailing circuit, which in turn heated and melted the dizzy button."

Wow that's deep. Thanks DD. You know that might explain why that trailing plug hole in the rear rotor is a mess and won't accept a plug anymore.

You guys are smart, I owe ya'll a beer.

CSI: Intarwebz

nothing a couple of brains cant figure out :)

i once had a similar problem. it didnt end up destroying the engine but it did make a nasty nois. this lasted a couple of days driving the car, progressivly getting worse and i just couldnt take it. i looked at some other things first and then pulled the cap. suprisingly the engine was still running ok. here are the pics of what i discovered:

http://i636.photobucket.com/albums/u...b/DSC07206.jpg

http://i636.photobucket.com/albums/u...b/DSC07205.jpg

i'm still intrigued by this, the last couple of days i've noticed slight hesitation on take off, also more backfiring than the usual and a jumpy tack, so today i started looking around my plugs and wires and this is what i found:

http://i88.photobucket.com/albums/k1...08-09_2015.jpg

car's still running good, idle is good. i just replaced this like 5 months ago i think... my leading plugs were nice and brown, but trailing were quite black, which i'm guessing is from a weak spark due to the burnt rotor. timing is where it should be set to.......:dunno:

Whooo hooo, that rotor button looks just like mine, it must still be good. Glad I didn't throw it out!

it's actually two of them, diagonally so if you were to trace a line through them it'd form an " X " right down the middle lol.

i took it out and installed the one i had in there before, it was good only reason i replaced it was because i'd owned the car for 3 years and had never changed it, so i don't know how old it is lol.

Yours looks like it has the same problem as mine, melted plastic that looks like a bullet got shot through it, probably caused by arching at the electrical contact inside. The difference of course is that mine was associated with a rotor going bad, which could have caused the rear trailing plug to ground out.

Yours is still functioning in a running motor, I wonder what caused it to do that?

ray, on our camry we didn't replace the cap and rotor and it messed up the coil and the ignitor. it left me stranded 50 miles away from home.

now we replace the cap and rotor. its a much cheaper thing to do maintenance

This is turning into a very interesting mystery!

mystery of the drive-by rotor lol

We actually transplanted the dizzy from the White One that fostered that rotor button melt down into the Silver One today as part of our efforts to fix a problem in that car. It didn't fix the problem; I should have checked the rotor button for bullet holes, will do so first thing tomorrow morning.

took a look at my old aftermarket rotor and found this
http://i3.photobucket.com/albums/y89...oto062_001.jpg

i now bought a new one from mazda. although my old rotor was working okay, its a good inexpensive maintenance item to replace. also replaced my cap too with one from mazda.
http://i3.photobucket.com/albums/y89...oto061_001.jpg

The dizzy from the White One, which was in operation when that rotor button melted down, seems to be working just fine after I transplanted it into the Silver One, using another rotor button I had sitting around (not OEM, but in reasonably good shape). Here's the Silver One idling with the White One's dizzy with the fried rotor button replaced:

http://i259.photobucket.com/albums/h.../th_silver.jpg

We are working on that overly expressive exhaust system today to quiet it down some.

So I'm guessing in my case at least the melt down was caused by the rear rotor failure, as predicted by the dizzy gurus in the earlier posts, probably due to grounding of that rear trailing plug by a piece of the apex seal (what a brilliant analysis, I want to believe it's right even if it isn't!)

But I agree with boyee, the Mazda OEM cap and rotor are probably worth the small fortune that Mazda (and Mazdatrix) gets for them. They have the brass terminals in the cap instead of the aluminum terminals you get in the aftermarkets and they just look prettier, as you can see in boyee's photo above. Thanks for posting, I'll order today!

Hope I'm not too late to say thisbut if you're going to order from Mazdatrix be sure to ask them if it is a genuine Mazda part. I've been deceived a few times getting aftermarket branded part when I thought I was paying for a more expensive OEM part. Just my .02