I’ve bought a “new to me” series 3 that has an xr700 ignition, trying to get it to run after an extended slumber. I’m getting 4.5 V to plus side of coil under “run” and 9V under crank. Put on a new SNG ballast and Lucas 1.5 ohm sport coil, checked and rechecked all wiring and still same result, the XR700 says I should be getting 9V under “cranking” but with ballast systems I was always pretty sure it was 12V under crank and 9V on “run” any help would be appreciated.
Ps, I can get the car the catch and run very briefly w/starting fluid, I’m trying to start with just a gravity feed can hanging above the carbs, I may need to go with a pump fed remote tank (tank in car needs replaced)

 

The whole point of a ballasted ignition system is that when starting the full voltage is applied to the coil, but this will never be the battery voltage, as the starter motor, running at the same time, reduces the voltage. That's why your lights dim if you start the car with them on. I would expect the coil to be rated at 6V and whilst cranking the maximum volts available is supplied, which will be higher than 6, but less than 12. When the engine starts and cranking stops, the ballast coil is switched in to reduce the voltage at the coil. Withuog this it would burn out quite quickly

 

Makes sense, my TR6 is ballasted and I’ve never really checked the voltages. I’m getting good spark on the Etype so I’m going to focus on fuel delivery at this point… as a wise man once said, all suspected fuel issues are really ignition related and all suspected ignition problems are fuel related 😉