I used to spend at least an hour of classroom time on the history and design of electric starters. The Cliff's Notes version goes like this: Starters operate at what is essentially a dead short- - - - -resistance down in the 1/100ths. of one ohm. The only thing that controls the current flow in a starter is something called "Back EMF", the tendency of a spinning armature to generate a voltage opposing the current flow to ground. The slower a starter turns, the more current it draws from the battery. Since electrons follow the path of least resistance, if the starter is hogging all the current, systems like the lights, ignition, etc. don't work at all or at least they don't work well. It's like following the fat, greedy guy down a buffet line- - - - -you might leave hungry!
Trying to run an ignition system while a slow-turning starter is sucking up all the juice is like trying to water your lawn when there's a big hole in the water main out in front of your house- - - - -the pressure just isn't going to be there to run the sprinkler. It's vitally important to make the starter turn as fast as possible so there can be some voltage left in the battery to power other systems.
Jerry
