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Shorting that wire to ground by itself will not cause the wire to burn out if it was in good shape. That wire is the current path from the low side of the coil to earth. When the points are closed... it's the equivalent of that wire being shorted to earth.

The question is, how much current is flowing and is it too much. If you have a standard coil (a non-ballast, nominal 3 Ohm coil) then closing the points and/or shorting that wire to earth will only allow about 4 Amps to pass. That will make the wire warm but it should not melt. I doubt you have a ballast coil installed but if you did, and if that coil was running without a ballast resistor, it would allow too much current to flow through the distributor and then the wire could get quite hot.

For future reference, do not use just any bit of wire to replace the one that burned out. It is supposed to be a high-flex wire that allows free movement of the breaker plate under vacuum advance. Buy a new proper lead or visit a motor shop and buy some used brushes with similar wire that you can salvage and solder in place of the melted one. Coat that wire with a bit of the woven fiber insulation sleeving used in place of plastic insulation.

Look at the insulators on the points as I (and others) have suggested... they should be on the threaded post with the nut shown in your picture. The assembly order should be, threaded stud, nylon bushing, points spring, condenser ring terminal, ring terminal for wire going to the coil connection (your burned out wire), second nylon bushing, nut. Refer to the picture below. (Sorry the picture is big... I just grabbed it from the net).



Others have listed the wiring above but I will repeat it below. This is for positive earth.
Positive battery lead connected to the engine block.
Negative wire from the battery to the coil SW terminal.
Wire from the coil CB terminal to the plastic lug on the side of the distributor.
From there the current will go through the replacement wire you install in the dizzy to the moving arm of the points via the spring. The path to earth is completed when the points close. The condenser is also connected to the points spring so it is "charging" when the points open.

Again, the damaged wire inside the distributor should not have melted from a short to earth as that's what the points do... they create a short to earth. However, if that wire was partially broken, the current could have burned through what was left of the conductors.

Nice one thanks doug.

Picture makes it easier to follow. The piece of wire is a temporary fix just to get it running. I want to strip/clean/renew most of the service items anyway as being sat for 20 years hasn't helped. I wonder if the wire was as you say partially broken anyway and this has led to it breaking?

I'm going to get new points and condenser and the rebuild things back up as per the photo then I can make sure things are in the right order.

Hopefully this will get the required results then I can move onto the carb (something I'm much more comfortable with than electrics)

Cheers

Alan

Th4neuk wrote:I want to strip/clean/renew most of the service items anyway

Beware of "chocolate" rotor arms... (Keep your old one!)

viewtopic.php?f=3&t=10679

Ian

Alan
DO NOT THROW ANYTHING AWAY THAT YOU REMOVE, The reason , A lot of the repro stuff is inferior ( SHITE ), I made that mistake while doing a resto , fitted all new dust/ grease seals ect, Thrown every thing away and now i have got to strip it all down again including the front suspension to fit seals, They also say that the new in a box with Lucas name on condenser are rubbish, Try and buy NEW OLD STOCK ( at a price ) or refurbish what you have or second hand ,
Hope this helps , Were are you in Lincolnshire ????????

Goff

Well points are shot as the red plastic bit that goes against the cam looks a bit melted. Not sure about the condensor. Tbh the rotor arm looks ok so might keep that then. Dizzy cap may clean up and contacts inside are a bit grotty but again may clean. I'll be guided by you all and keep everything then. I think a lot of the rubbers are going to need to go as well as looking round the car they seem very perished.

Goff am near the humber bridge

Cheers

Alan

Woohoo thanks guys. Gave all the electrodes in the dizzy cap a clean with some emery paper and double checked the posts as per the picture etc and all looks well. Any connect all up and we have a spark. Downside is i need to charge battery. I've sripped the carb and gave it a prelim clean (run out of carb cleaner though) so now just need to get some petrol and give it a whirl. Am charging the battery overnight so fingers crossed for tomorrow night

Thank you all for your help with this

Cheers

Alan

Excellent! It's an exciting and nervous thing starting an engine for the first time. Let us know how it goes!

I do hope it all goes well & I must confess that thinking about it, Doug is spot on about that burned wire, it can't happen if all is as it should be, so I apologise for my mistake, I hope that didn't mislead you.
Rich.

Melted points + Burned Wire = (Possibly) - Someone's tried/used a ballast-type coil by mistake...


A 12v coil should be about 3 Ohms. If the coil is about 1.5 Ohms,
it's probably a ballast type and would need a resistor in series.

Ian

After replacing points, condensor, Low tension lead (the burned out wire), new plugs and getting the firing order right i rigged the fuel amd she started. I have got a new coil to go on as well but might leave that till it all goes back in.

Thank you everyone for the good and helpful advice.

I'm sure many more questions will be heading your way

Cheers

Alan