Ignition Coil - 12V or 6V

[Mervyn Waugh]

Triumph V8 with Lumenition ignition. Normally a very smooth running engine, however I am getting a slight misfire at even throttle (1500 - 2000 revs) after the engine has been running for a while. Plugs are fine, good colour and the rest of the ignition system seems fine too. The coil is labelled '12v standard' but there is a pink/white & white/yellow connected to the positive terminal. Should I be using a 6V ballast coil, and could this be the cause of my misfire?

[StagJonno]

Sounds like your wiring is as original and requires a ballasted-type coil. The White/ Pink wire is the ballast resistor; the White/ Yellow wire is from a contact in the starter solenoid that provides the coil with full battery voltage during cranking (compensating for the reduced battery voltage when the starter motor is running).

If you have a multimeter, you could measure the resistance of your coil, after removing the low voltage connections. A ballast-type coil will have a resistance of approx 1.5 ohms; a 12V (un-ballasted) coil will be approx 3 ohms.

Worth checking that the connections are sound. Vibration over time can cause strands to break.

Coils can break down as they get hot, especially if old. Also ensure the coil is held securely in its clamp and the bottom is clear from the engine block, to reduce the amount of heating from the engine.

[Goldstar]

Yes and maybe.

[jbuckl]

Reinstate the ballast system; use a viper resin ballast coil. (Other coils are available… e. G. Bosch red top… but can be unreliable)

electronic ignition needs a separate supply for best reliability…. Not piggy- backed from fuel pump inertia switch or coil supply. ( although they work, they can steal current at the crucial moment for a stable ignition)