Triumph Repair: Ignition Coil, triumph spitfire mk 4, triumph spitfire mk

Question
Hi,
1973 Triumph Spitfire Mk.4 1500  FM5333
Tuned up car and changed coil,car will not fire now. put on a 12 volt coil. Coil says  12v ballast
on it. There is no ballast resister on the car.
Should I have a 6 volt coil with or without a ballast resister or 12 volt? Would this stop the car from firing? I dont know what volt coil was on the car before.  THX. Much! I live in Iron Mountain,Mich. 100 mi. north of Green Bay,Wi.  

Answer
Richard,

I'm currently 1500 miles from my trusty reference materials, let me see how I do from memory.

On some model years Triumph used a piece of resistive wire for the main power feed to the coil, with a plain wire bypass hooked into the starter circuit.  In other words, when the car is running the coil is fed from a 6 volt feed via the resistor wire.  When you turn the key to start the engine the normal copper wire is energized and the coil sees whatever voltage you have in the battery.... hopefully greater than 6 volts!

The extra voltage gives the spark an extra boost for starting.  Having the full battery voltage only while starting prevents burning out the coil by overheating it

I believe that to be the case for the '73 model year Spitfire.

So nominally, you'd want a 6 volt coil.

Here's the fun part.  A 12 volt "ballast" coil might be indicating that it was designed for a 12 volt system running the 6 volt/12 volt split.

Even if it's the wrong voltage coil, there should still be some spark when you turn the engine over.  A simple test would be to pull the coil-distributor lead from the distributor and set it where you can see if you get spark when you crank the engine.  The area near the brake/clutch masters seems to have a few possibilities.

If you get no spark whatsoever then you need to start troubleshooting the entire distributor circuit.  Is the hot side of the coil getting any voltage with the ignition on?  Are the points clean and properly gapped?  If you still can't find a fault, there is the possibility that the coil may be bad, regardless of what voltage it should be running.


Let me know if you need more assistance.


Cheers,

Jim