Morris Minor Owners Club

A funny thing happened to me on the way to the council dump yesterday .......
I made a fairly tight (and quick) u-turn to join the queue for the dump and the Minor stalled. As she is very reliable I was a bit puzzled, which evaporated when I smelled burning wire.
Checked under the bonnet and the wire to the coil from the fuse box was bare copper, the insulation having metamorphosed into a nasty smoke. When I cleared it away from the body work, the car started and got me into the dump enclosure. The helpful council guys gave me some wire and tape and I made a safer repair to get home.
Three hours later and lots of new wiring to and from the regulator, ignition switch and coil we were nearly ok. Except, no brake lights.
Looked around the brake light switch and found a green wire (is this the season for green wire problems?) cut very neatly in half. Connected it and the brake lights work.
Now we get to the point of this story .... it's no good fixing a sympton and I am trying to work out why the ignition circuit burnt out. Its also no good having a sloppy wiring loom !
Either there was a latent earth in the wires that burnt up, or...
the violent u-turn jerked the wiring loom under the rad into the fan blade - cutting a wire neatlyand earthing it. Could this have affected the coil and ignition switch wires?
She runs well now and everything works except the horn (tomorrow's job). Oh, the horn did work as I used it about a half mile before the fire.
Any ideas please? Is my fan theory just too desperate?

Paul,

If the wire was completely bared all the way to the coil, then it was earthing there, as it will only melt the insulation up to the shorting point (and a little bit after). best to check the coil in that case

Are you sure your brake lights were working before? does the cut look recent or is there some dirt on the end?

I can't see how the brake light feed would affect the coil, as it is in a different part of the loom.

The insulation may have worn through on some of the wires and contacted earth that way, have a look on the bodywork in the surrounding areas for little tiny 'spot-weld' marks.

Cam, Thanks!
The cut on the wire was brand new and perfectly clean. So good a cut that I am wondering how to use the fan blade to cut the lawn!
The wire was burnt nearly bare from just by the fuse box to the coil! both ignition circuit wires to the ignition switch were also damaged with melted insulation. I only just had enough heavy wire to replace it all. The fule pump wire was ok, it seems just to have affected the larger wires in the loom - can't really see as they are bound up by the loom cover!
I still have to look at the horn but apart from that all seems well.
After a couple of days thinking I suspect that there must have been an earth to the body - I will have a good look for scorches as you suggest.
The idea of earthing through the fan blade a a little far fteched I now think.
The brake lights should have been working before (my son and wife use the car too and I try really hard to ensure that they don't break down).
So it could be that the violent turn just made an earth to something via a bare patch on the wire, it "welded" itself briefly giving a better connection and hey presto! burnt out wires!
I will look and report.
Another post on the site mentions the breather to the carb and lean mixture - I disconnected this as the air filter was getting very quickly
oiled up. The car runs fine, so should I blank the stub pipe off and recheck the tune? Or leave it alone?
How is a coil checked? I have never done this. This one is a few years old and has been very reliable!

should I blank the stub pipe off

Yes, it sounds like you have increased the mixture to conpensate for the extra air, which is OK at low RPM, but it will lean out at high RPM. So, blank it off and retune the mixture and idle.

If the wire has burnt out all the way from the ignition to the coil (and no further )i.e. not into the dizzy, then the wire connection to the coil is suspect, or possibly the coil has an intermittant shorting fault!

The best test for a coil is: is it working!! you can meter the coils and compare the values with those listed a manual (I can't seem to find any listed at the mo), but that won't show intermittant faults.

To be honest, I would replace the coil with a new one just to be on the safe side. Do the coil terminals look like they have been part of the action??

The coil terminals looked unaffected - and it works fine. This coil has two spade connectors on each terminal and as a failsafe I connect each wire to both (once had an irate wife who stalled because a coil wire fell off!). The wire close to the coil was ok - probably misled everybody a bit when I talked about bare wire.
Still haven't been able to inspect yet (Mothers Day, children exiting and returning to the nest!) but I will!
This weather makes we want to convert to a soft top!

A little embarrassing .......... I had not reconnected the horn live feed (regulator box to fuse box). My excuse is that it is the rear row on the regulator and hard to see! Works when connected!
No scorch martls etc - so original cause undetermined. Anyway all seems fine so thanks for the help!