This blog, in addition to the usual maintenance details for classic mini cars, an attempt is made to explain the "whys" and "wherefores" of the various jobs.

Thursday, 15 October 2009

High-tension Leads

On the high-tension side of the ignition system we are dealing with high voltages which will "flash over" or take the line of least resistance whenever possible. The high-tension leads between the coil and the distributor and between the distributor cap and the sparking plugs must, therefore, be tested at intervals by doubling the cable between the fingers and examining the surface for the tiny cracks which indicate that perishing has begun. Alternatively a soft, swollen appearance of the insulation is characteristic of the deterioration caused by the action of oil or petrol. The modern plastic-covered high-tension cables, which are much more resistant to either form of failure, should always be chosen when the leads are renewed, although rubber-covered 7 mm ignition cables may still be offered by some garages.
To fit the cable to the central terminal of the ignition coil, remove the brass washer from the end of the old cable, bare the end of the lead for about i in., thread the cable through the terminal, pass the strands through the washer and bend them back so that they will be gripped when the terminal is screwed into the coil. In the distributor cap, on the other hand, the cables are retained by pointed screws that pass through the electrodes in the interior of the cap. When fitting new cables, therefore, the ends need not be bared: simply remove each screw, push the cable well home until its end is visible at the base of the screw hole and then tighten the screw firmly so that its pointed end will pierce the insulation and make good contact with the strands of the cable. Give each lead a tug to make sure that it is held securely.