Triumph Repair: Replaced all ignition - still no spark!!, ballast resistor, brake master cylinder

Question
Really hope you can help me, I'm utterly, utterly dejected here!

I'm having huge problems trying to get a spark of any kind from my Spitfire (its a late 1500 with the ballast resistor built into  the wiring loom).

Here's what I've been through...

Replaced - coil, plug leads, plugs, dizzy cap, rotor arm,  condensor, points & now battery.

I've checked voltages with a multi meter and here's what I'm getting..

Voltage from battery to solenoid - 12.3V

Voltage coming from ignition/solenoid to coil positive terminal is 6V with ignition switched on.

Voltage coming out the end of coil lead is 6V with ignition switched on.

Voltage coming from the end of the coil lead with the engine cranking  is 8-9V - although when I hold the end of the lead close to the  engine block, there is still no spark arcing across.

I've tried hotwiring the coil thereby bypassing the ballast resistor, giving a full 12V on the positive terminal of the coil, voltage  coming out of the end of the plug lead is still 8-9V whilst cranking,  but still no spark.

When I'm hotwiring the coil and putting the power to the positive terminal, it crackles and sparks a bit until the spade connector is seated properly.

I've cleaned all the earth terminals until they're shiny!!

I'm really at the end of my tether now with this, if you've got any  ideas as to what's going wrong I'd really appreciate it!


Answer
Ewan,

You neglect to mention whether the car is still fitted with the factory Lucas ignition system or whether it's been replaced with an aftermarket points replacement system such as Pertronix.

With the stock Lucas sytem and everything wired up correctly and in good shape you'll get a spark from the coil (verified by setting the high tension lead from the coil so you can see a spark to ground... the brake master cylinder bracket makes a good spot) when you turn on the ignition and remove the lead from the ballast resistor.

The coil is a transformer, converting low voltage (12v) high current into high voltage (20,000 volt +) short duration sparks.  There is not a direct wiring connection between the low voltage connectors and the high voltage output, it's magnetic induction that "makes the spark".

From your experimenting it sounds like you might have burned out the coil by apply voltage improperly.

What are you using for a shop manual?  I personally recommend the Bentley manuals, they have a very good troubleshooting section for the late Spitfire.


Cheers,

Jmi