Is it the starter or the battery?

[Michael A.]

Need some help on the diagnostic procedure I should use to determine if I have a battery or a starter problem. Here's the situation:

• 66 small block, 327/300
• 9 year old rebuilt starter, approx 30k miles since it was rebuilt.
• approx 7 year old battery with disconnect switch mounted on positive terminal
• when I turn the ignition (engine cold or hot), it turns very slowly and may or may not fire up
• I have cleaned the battery terminals and fully charged the battery. Battery measures 12.5v after charge.

I'd appreciate suggestions on what I should check to determine if it's the battery, starter, both or something altogether different I should be checking.

Thanks,

[William C.]

Re: Is it the starter or the battery?

Many things to check, but I'd start with how does the battery voltage hold up UNDER LOAD? What does the voltage drop to when cranking might be a good number to know regarding the health of a 7 year old battery.

[Michael W.]

Re: Is it the starter or the battery?

Try jumping the battery from another car. If the engine spins at a higher speed, it's not the starter.

[Michael G.]

Re: Is it the starter or the battery?

Let's see....car driven sparingly, 7 year old battery......surprised battery has lasted this long. Do not see the starter as the issue. If your in doubt battery is the culprit, start car with another battery. Believe you'll be shopping for a new battery.

[Michael A.]

Re: Is it the starter or the battery?

Thanks for the tips all. I followed the suggestions and here's the results:

- Jumped started it and the starter spun faster
- Checked voltage drop when the ignition was turned - voltage dropped to 4.5v

Sounds like it's the battery.... a much easier item to replace. Any other items I should be checking before I head out to purchase the new battery? Suggestions on brands?

[Michael A.]

Re: Is it the starter or the battery?

Let's see....car driven sparingly, 7 year old battery......surprised battery has lasted this long. Do not see the starter as the issue. If your in doubt battery is the culprit, start car with another battery. Believe you'll be shopping for a new battery.

Michael
Yup it's an old battery but I just replaced the original battery in my 2003 daily driver with 165k on the odometer. A battery would be far easier to replace than the starter.

[Bruce B.]

Re: Is it the starter or the battery?

I like the AC Delco batteries. Probably now made in Mexico but I have great performance using them for many years and still have a few 4 to 7 years old that work as designed.

[Terry M.]

Re: Is it the starter or the battery?

We have visited this subject recently;

https://www.forums.ncrs.org/showthread.php?97702-93-Battery-Drain

https://www.forums.ncrs.org/showthread.php?97782-More-on-Batteries

[Michael A.]

Re: Is it the starter or the battery?

Hi Terry
Thanks for the links. I had found the second thread when I did my search before posting but not the first. Lots of good info in both but I was looking for the right troubleshooting steps. As always, I got some great assistance from the TDB. I now have a new battery installed and it's cranking great!

All of the folks on the TDB are a god-send to people like me. The wealth of experience gives me the ability to keep my car running and keep me smiling. Thanks to all!

Cheers

[Michael W.]

Re: Is it the starter or the battery?

Glad to hear that it was an easy fix.

[Terry M.]

Re: Is it the starter or the battery?

Mike,
I was replying to your "Any suggestions for brands?" comment. I thought those two threads about sums it up for brands. I guess I could have/should have made that clearer.

[Paul J.]

Re: Is it the starter or the battery?

Don't over think these things Mike. Just remember that it takes amps to turn the flywheel. A battery that shows 12 volts may not have any amps, and this is usually the case.

Sometimes a duck is just a duck.

Paul

[Michael A.]

Re: Is it the starter or the battery?

Thanks Paul. This duck was definitely quacking. I just wanted to make sure I was hearing it right

For me the thinking part is a big part of the fun. I don't do this stuff every day so the TDB is my go to source to help me think things through. I fully understand your comment about amps I just didn't know how to measure the amps. The suggestion of jumping the car to see if the starter turning faster (which it did) confirmed that the starter was not the problem. So by simple process of elimination, it was clear that the battery was the source of my trouble. The new battery did the trick. I hope it lasts as long as the last one did!

Cheers,

[Michael A.]

Re: Is it the starter or the battery?

You're a star Terry. Thanks for the help. I definitely love the "search" function and the wealth of info on this board. It is amazing!

Cheers

[Terry M.]

Re: Is it the starter or the battery?

Thanks Paul. This duck was definitely quacking. I just wanted to make sure I was hearing it right

For me the thinking part is a big part of the fun. I don't do this stuff every day so the TDB is my go to source to help me think things through. I fully understand your comment about amps I just didn't know how to measure the amps. The suggestion of jumping the car to see if the starter turning faster (which it did) confirmed that the starter was not the problem. So by simple process of elimination, it was clear that the battery was the source of my trouble. The new battery did the trick. I hope it lasts as long as the last one did!

Cheers,

Mike,
There is a third player -- besides the starter and battery -- the wires and connections. Without good clean, tight connections and wire of adequate size one can chase ones tail around on a hard start issue.