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MG TD TF 1500 - Ignition Failure from Carbon Brush

See http://www.ttalk.info/Failure.htm for images about the events mentioned in the somewhat cryptic thread about the nail, shoe, horse, etc. Bud


Bud Krueger (TD10855)

Dis it break off Bud or is it shoved back in the cap? I wish they still made the caps with the brass posts. Looks like one of yours has some good burn marks. How many miles on it? Moss replacement?
LED DOWNEY

I am also courious about the one post that is really "toasted" ,,,, what would cause only one post to get this way??? A wobbley shaft would cause wear instead????

SPW
Steve Wincze

Bud, I bet this was due to the Petronix. On both my TD and very recently on friend's TC, we had the following issue: the magnet collar on the Petronix does not allow the rotor to seat all the way. On both cars, the cap perceptively "rocked" when trying to clip it down. If it was clipped, the rotor was smashed into the center of the cap. Yours looks exactly like what would have happened if we hadn't noticed that and driven the car. Both of us had original Lucas emblemed caps, and different brand of rotors. The fix was to file about 2-3mm off of the bottom of the rotor. You can use a piece of soft wax or similar to check clearance, remove the carbon brush first. George
George Butz

Nice analysis George!
Dave Braun

Hopefully, this evening I'll get a chance to have a closer look at the components. I'm anxious to see if the spring is still up there behind the carbon.
You may recall a thread from a couple of years ago in regard to the pertronix sleeve and various rotors. I did an analysis at the time and showed dimensions of various rotors.
Will have to dig back in my log to see when that cap was installed. Pertronix is so trouble free that I very seldom have reason to remove the cap. Discovered a 2-pack of red rotors in a parts drawer. They're about to make it into Lazarus' travel package for trip to Mystic next month.

More later --Bud
Bud Krueger (TD10855)

Bud,
Years ago I had a rotor tear up the inners of my MGB cap because the magnetic coller of the pertronixs sat too high...I have routinly shaved about 2mm off the bottom of the rotor ever since...no problems...same pertronixs in the B for 15 years and in the TD for 6 years...FWIW...the collers are to high....
Bob Dougherty

Here's a view of what was going on inside of the distributor. The Pertronix sleeve caused the rotor to completely compress the carbon brush and then put pressure against the center of the cap, wearing it away. I'm about to put a series of images on Ttalk showing more of this.
A work-around for those of us who are fond of the Pertronix Igniter is to shave about .030" off of the bottom surface of a rotor. Bud


Bud Krueger (TD10855)

The images are at http://www.ttalk.info/Failure.htm Bud
Bud Krueger (TD10855)

This thread was discussed between 31/08/2010 and 10/09/2010

MG TD TF 1500 index

This thread is from the archive. The Live MG TD TF 1500 BBS is active now.