On Wednesday, April 10, 2019 at 9:51:40 PM UTC-4, Clare Snyder wrote:
On Wed, 10 Apr 2019 13:22:23 -0700 (PDT), TimR
wrote:
I'm throwing the bull**** flag on this. It has always taken more power to turn an engine over mechanically than to get a spark plug to fire.



Yes, that is true - but you can run the flag down the pole. If the
battery "sags" from the cranking current there is not enough VOLTAGE
left to make a good spark. That's why on Kettering ignition (typical
points and condenser type of years gone by) there was often a ballast
residtor that ewas shunted out of the circuit for starting. The coil
was designed to run on 7 or 8 volts - about the voltage available from
the battery when cranking a cold engine. Once running the resistor in
the circuit limited the coil current to what it would be at 8 volts.

This was done because a 12 volt coil running on 8 volts coukld not
fire the plugs reliably.

Huh. I spoke too soon. I can see how cranking could drop the voltage enough to cause other problems, I hadn't thought of that.

I will fold that flag and save it for later. Shouldn't need to wait long, with this crowd.