Burning wire! Horror story.

[davidball]

Tried to start the cat 2 hours ago and got a very sluggish turnover. Having just replaced the starter I was mighty p*ssed off. So I put the battery on trickle charge and tried again later. A slow turnover again but this time accompanied by whisps of smoke and the smell of burning rubber. A wire in the loom had melted its insulation. See pictures
http://img379.imageshack.us/img379/6548/imag0036tl...
http://img379.imageshack.us/img379/871/imag0035zv0...
http://img379.imageshack.us/img379/7961/imag0034ng...
I unwrapped the loom and traced the wires path. It connects the neg battery terminal to an earthing bolt on the bar that supports the headlamps. I stripped out the wire and the car started first time. I checked all the guages and switches and everything is working. Wierd. Any ideas anyone?

[thinfourth2]

If it goes from the battery negative to the headlight bar then it must be a separate earth for the headlights. Which is odd.

Anyway to get big amps down that then the amps returning from the starter to the battery must of got lost. So check your battery negative to car chassis / engine block cable

[davidball]

Many thanks for the advice. I will take the strap off and check the connection.

[GreenV8S]

The ideal setup has an earth loop rather than a single earth:

battery to chassis (provides earth for all the minor stuff)
engine to chassis (earths the starter via the chassis earth)
battery to engine (earths the starter directly)

With this setup, two out of three have to fail before you have any problem. This arrangement used to be quite common back when starter motors and batteries were marginal and would routinely let you down unless everything was just right. These days less necessary but still a darned good idea.

[davidball]

Thanks for the advice. I have removed and cleaned all earth connections, replaced the cable and added a 16 amp line fuse. It seems ok now. My troubles started when I tried fitting a Bosch electronic dizzy. It would not fit properly so I put the Lucas one back in and when setting the timing the starter failed. After a two weeks search I got a recon starter, fitted it and almost set fire to the loom.
I think I will leave the Cat alone for a while.

[JB Rugby]

davidball said:

Tried to start the cat 2 hours ago and got a very sluggish turnover. Having just replaced the starter I was mighty p*ssed off. So I put the battery on trickle charge and tried again later. A slow turnover again but this time accompanied by whisps of smoke and the smell of burning rubber. A wire in the loom had melted its insulation. See pictures



I unwrapped the loom and traced the wires path. It connects the neg battery terminal to an earthing bolt on the bar that supports the headlamps. I stripped out the wire and the car started first time. I checked all the guages and switches and everything is working. Wierd. Any ideas anyone?

nothing constructive to add. just glad it didn't end up in tears!

[davidball]

GreenV8s. Thanks you were right. The car has an engine to chassis earth and an engine to battery neg connection but the battery neg to chassis (the one that melted) is for earhing the headlights and not able to carry the kind of current required by the starter. Even though I have cleaned both engine earth straps the current was still flowing through the headlight earth. I am glad I put a fuse in it. Anyway I have used a suitable cable to connect the battery neg to the chassis and so far all is well.