MG Roadster 1973 - Coil problem

[Dickie Dastardly]

Afternoon,

I have a colleague who has a lovely 1973 MG Roadster but is having issues with the coil overheating. The car will eventualy misfire then cut out, it will not restart until the coil has cooled down (at the point of cut out the coil is so hot it cannot be touched).

Has anyone experienced a similar problem?

Thanks

Richard
NB the car is fitted with electronic ignition.

[Richie Howard]

I had the same issue after switching to Lumenition.

I swapped the (quite new) coil out for their (quite expensive) job and it seemed to sort it.

[v8250]

This could be a number of things. Common fault is that some owners turn their coils so the connections are topside; this should not be done as the coils uses its inner oil as internal cooling. It may simply be a new coil is needed as the existing one is breaking down under load. The coil could also be suffering from 'tracking' or arcing...this is where there is some resitance to output on the HT side i.e. resitance via HT lead to spark plug and the output charge needs to go somewhere. Ask your colleague to check ignition in the dark to see if there are any external sparking 'tracks' and to ensure all HT leads are correctly fitted + have no high resistance end to end. Also, make sure the points gap has not closed up and the timing under dwell is correct. Check quality/install of LT wires to/from coil and distributor. All the above will cause the coil to overheat.

Lastly, there can be an odd fault that causes the coil to overheat...this being the HT lead rubber boots [here I'm assuming as the car's a 1973 he'll have push-in connectors]. Some rubber boots simply do not 'sit' correctly. This causes the HT connector to not be pushed home completely and therefore have intermittent/higher resistance to contact; this scenario can be a pain to diagnose. The trick is to spray a little WD40 into the boot before fitting, firmly push home the connector and boot, then lift the boot to expel any air trapped inside the boot. This will ensure a good clean/tight fit.

Good luck to your colleague...

[Dickie Dastardly]

Thanks for the feedback, i'll pass this on.

The owner (Archie) is 67 and is retiring in a few weeks, he'll be delighted with any advice that may help.

Cheers
Richard

[v8250]

Dickie Dastardly said:

Thanks for the feedback, i'll pass this on. The owner (Archie) is 67 and is retiring in a few weeks, he'll be delighted with any advice that may help. Cheers Richard

Richard, fingers crossed for Archie sorting this out. If he really gets stuck ask him to call/contact the local MGCC guys near to you. Most are a real good bunch readily at hand to help. See www.mgcc.co.uk