One very useful test we used to do when diagnosing slow/no crank symptoms was a "series resistance test"- - - -done with a low reading voltmeter, not an ohmmeter. Using the 0-2 volt scale on a Sun analog voltmeter, we would check individual voltage drop across every conductor and connection in the cranking circuit, hot and ground. Dropping more than 0.1 volt across any connection while cranking on a 6V starting circuit indicated a dirty or loose connection, and any voltage drop at all from end to end of a battery cable or ground strap was reason for concern. 12V systems had a wider tolerance- - -0.2V drop per connection, and 0.1V for conductors. I used, and taught that procedure for over 30 years.
Jerry
