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 Posted: Oct 18, 2017 09:37AM
 Edited:  Oct 18, 2017 02:46PM
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This is a known problem with the after market rotors and has been on going for a number of years, I was told by my supplier that the material used for the rotor body is a clear or murky colour, so to make them more like the original they are coloured with a black material. They chose to use a CARBON based dye to do this which worked well until the amount of dye exceeded a certain level and they became conductive! The problem ones are those that start out OK but as they heat cycle become conductive and fail in use.

As an aside it's easy to test the rotor by pulling the cap and removing the coil lead from the cap, then have an assistant crank the engine over (Ign. On) and hold the end of the coil lead over the top of the rotor with a small gap, it should not spark. If it does it means the rotor is supplying a ground path to the distributor body and is NFG.

The updated and more costly ones are red in colour.................. Why do they cost more?...........Because they work.......

As an idea of how dangerous this can be, I was pulling out on the main Hwy in my 73 MGB GT when the rotor failed without warning, no splutter just dead. I narrowly avoided disaster because the twin trailer grape hauling truck driver was fully awake and took to the verge to avoid me. His words of advice about my piece of sh*t vintage car still haunt me!

Strange I wrote my reply thinking nobody else had replied as nothing except the original post showed? Now it's all showing I see that the question had already been answered..................................

Mini's are like buses they come along in a bunch

 Posted: Oct 18, 2017 08:16AM
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CA
Quote:
Originally Posted by dklawson

I still cannot see responses to this thread until I enter edit mode.  Very strange.

Mark, the only wires that should be inside the distributor are:
The wire from the moving arm of the points which goes to the coil,
The wire from the moving arm of the points to the condenser, and
The wire from the breaker plate to the distributor housing.

The breaker plate wire is a ground connection.  It can touch anywhere inside the distributor housing as long as it does NOT touch the moving arm of the points or anything connected to that arm.  If it touches there it provides a short to ground for the points and coil... like a kill switch, and you won't get any spark.

...or if it isn't well grounded where it should be, you'll also get mis-fires and starting problems. (Been there!)

.

"Hang on a minute lads....I've got a great idea."

 Posted: Oct 18, 2017 08:09AM
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US

I still cannot see responses to this thread until I enter edit mode.  Very strange.

Mark, the only wires that should be inside the distributor are:
The wire from the moving arm of the points which goes to the coil,
The wire from the moving arm of the points to the condenser, and
The wire from the breaker plate to the distributor housing.

The breaker plate wire is a ground connection.  It can touch anywhere inside the distributor housing as long as it does NOT touch the moving arm of the points or anything connected to that arm.  If it touches there it provides a short to ground for the points and coil... like a kill switch, and you won't get any spark.

Doug L.
 Posted: Oct 18, 2017 04:04AM
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Good to know the knowledge base is brimming with intelligent folks. I teach and Odyssey of the Mind class to kids from K-12. My daughter has done it every year since the 2nd grade. I try to teach them to NOT rest on the knowledge you think you have but to consider outside aspects of the problem. Think outside the box. When looking at this issue I knew brass couldn't become 'non conductive'. I didn't come to the answer but can see how my thinking was derailed by what I thought I knew.

My friend got an email from Jeff. Here is what he said:

I made the red rotors to eliminate 2 problems: 1. high carbon content of the black rotors was promoting burn-through and arcing to the shaft (ground) 2. the brass rivet was shortening the distance for that arcing to short to ground (and they're typically loose)

As a distributor rebuilder, I simply got tired of answering calls every day about stalled cars that were caused by failed rotors. After selling 60,000+ rotors, I have 3 known failures on my desk. 1 broken in half, two shorted internally from very high voltage systems with failed plug wires. I can live with a failure rate of .005%. Yes, half a thousandth of 1 percent.

You DO NOT need to replace these rotors as periodic maintenance. Just clean the edge with a file, scrape your distributor cap terminals with a pocket knife, and keep driving!!!

[email protected]

Mark Looman, Ada Michigan 1967 Austin Cooper S
 Posted: Oct 18, 2017 03:52AM
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THIS JUST IN! Someone on the MG Experience forum said the issue is the rivet holding the tab in place is allowing the current to detour back to the body of the distributor. After inspecting the side by side photos of the two, my rotor has a rivet that is enclosed by the black plastic while Blake's rotor has a rivet going all the way through and out the bottom. We also noticed a suspect wire in the distributor that is very fragile and may be exposed. Had we not gotten to the rotor figured out it was next on the list.

My conclusion to this situation is the wire or wires in the body of the distributor are causing it to short through the rotor with the exposed rivet. It's not one thing, it's a couple combined. I also wonder if there was a plug of material in the bottom of the rotor that degraded or fell out allowing it to short out. My distributor in my mini doesn't have that bad wire and it wouldn't run with the bad rotor? Hmmmmmm. More to learn.

Mark Looman, Ada Michigan 1967 Austin Cooper S
 Posted: Oct 18, 2017 03:44AM
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US
Mark, the problem you observed is not at all unheard of.  It has been going on for a few years as more cheap reproduction parts enter the market.

The typical failure mode is not an "open" as you discuss above but a "short".  When the rotor shorts, the electrical path is from that center contact point on the distributor cap right through the rotor to ground via the shaft in the distributor.  The electricity is never routed to the plugs... just straight to ground.  Fortunately you had an old rotor to experiment with. 

The advice given on many threads like this is to either buy replacement rotors from Jeff S. at Advanced Distributors or buy the blue epoxy rotors available from some parts suppliers.  As you observed, the rotor is not unique to the Mini so there are several sources for the blue rotors.

Sidebar:  In edit mode I see that Norm has responded with almost the same response as mine.  Oddly... I cannot see Norm's response when I read Mark's original post.  I only see Mark's first post. 

Doug L.
 Posted: Oct 18, 2017 03:16AM
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If it was a condenser or other piece of voodoo like ram for a computer or a moving part, I might be able to grasp the invisible flaw. But when a rotor worked, then didn't and there are no other factors like fit or corrosion I just don't understand!

Glad you posted this response. I will log that in my bank of things to look for if my car stops running!

Mark Looman, Ada Michigan 1967 Austin Cooper S
 Posted: Oct 18, 2017 02:55AM
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Not OT at all, the ongoing and common bad rotor issue affects us all.

if it wasn't a red rotor from Advanced Distributors, then the answer is, "they all do that".  The black rotors are not trustworthy and have not been for something like 20 years. Countless magazine articles and internet "discoveries" have covered this fact, over and over so much that it is still a surprise to find how many folks still haven't heard about it.

Jeff developed his, with proper quality control and materials used to maintain the quality, made it red and marked it with "AD" (there are some bootleg red ones which should be avoided as much as the black ones, they lack his mark).


N

 Posted: Oct 18, 2017 02:39AM
 Edited:  Oct 18, 2017 02:39AM
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This is essentially OT but we used my mini as the test bed, so it's mini related. My friend has a 1971 MGB. He's driving along, it sputters for a block or so, then shuts off. Won't start. We start the check sequence and find no spark. I get a test light and start checking to find the last point of electricity is at the little spring loaded tab in the inside of the distributor cap. It sits on the rotor just fine, the rotor is new, the cap is new. Stumped how it isn't getting to the wires I grabbed my rotor from my Cooper. It's the identical rotor, just dusty and corroded unlike the shiny new one in question. We drop my old one in and TADA the car runs. I swapped it back and it won't run. Below is a link to the video showing the bad rotor in my ignition to start, swap out my old one and it runs. We inspected every aspect of the bad rotor against my good one and can't find any possible reason. It's clean, It fits tight, and it's ONLY job is to move current from the middle to the outside of the tab. On a side note, he recently dropped the pin from his old distributor cap. You know, the spring loaded one that runs current to the rotor? The car ran like that for about a week before I spotted that issue. I assume it was arcing from the connection in the distributor cap to the rotor and allowing the car to run. We changed out the cap and rotor for a new one and the car ran great. Explain to me how current can jump a 1/4 inch but can't make it through a rotor that appears to be fine?

URL: https://youtu.be/Y3TQ71jF-00

Mark Looman, Ada Michigan 1967 Austin Cooper S