Engine just barely turning over - starter or battery?

[mcoomey]

Success!!!!

After making a series of measurements inspired by @nkaminar I concluded that the ground between the + side of the battery and the casing of the starter was soft. I added a cable directly between the starter mounting bolt and the battery terminal and now it cranks like a champ! Thanks, everyone, for your help.

For those interested, here are the measurements I observed:

* directly across battery terminals: 6.7v(open) & 5.4v(cranking)
* starter terminal --> casing: 6.7v(open) & 3.9v(cranking)
* battery + terminal --> starter casing: 0.0v(open) & 0.7v(cranking)

After adding the ground cable and cleaning up other connections:

* starter terminal --> casing: 6.7v(open) & 5.8v(cranking)

 

[David in San Antonio]

MCoomey - Thank you for posting the outcome. It’s always satisfying to learn how the problem was solved.

 

[Ayers1]

Glad you found the problem! Always happy to hear the solution!

 

[Rob Doe]

Mcoomey, congrats on your success!


As a parting thought, do you have the Les Andrews (blue), "Troubleshooting and Diagnostics" manual? Chapter two has information regarding the starting and charging system of a Model A. It is laid out in a logical order with drawings and instructions. A study of Chapter 2 would have made quick work of your issue.

 

[mcoomey]

do you have the Les Andrews (blue), "Troubleshooting and Diagnostics" manual?

Thanks, Rob. No, I don't currently have that book but it sounds like it would be a worthy investment.