11-06-2018, 01:22 AM
From what I have been led to believe, it doesn't matter. Or at least not that much. An ignition coil is basically a low voltage to high voltage transformer and because it is an alternating current device it is not affected by polarity. The spark plugs will give the same quality spark regardless of coil polarity but there is an interesting theory that says electrons prefer to flow from hot to cold so you would ideally have a potential negative voltage at the central (hot) electrode with a positive earth system. As you cannot be sure if your coil is designed for a positive or negative earth car you can determine for yourself which way the current is flowing. Detach a HT lead and place it near an earth point (or a plug connector end) with a graphite pencil tip in-between. Crank the engine and you should see a spark jump between wire and pencil, then to earth (or spark plug). There should be a flare between the pencil and earth (or plug). If the flare is going towards the coil the polarity should be corrected by swapping over the wires on the coil.