No power at all
I think from start. Sorry. Running off memory here. When you twist to start everything goes dead and stays dead like a dead battery, but the battery is full. Go back an hour later and get a dome light again but then all goes dead when you twist to start. Jumps fine like a ground issue. Just was hoping for an ah-ha moment on here. Haven’t metered anything yet.
In reverse order.
Ammeter
There's an ammeter in the instrument panel.
It shows the amount of current flowing to or from the battery, excluding the power to the starter.
When equipment is on, and the engine isn't running, the ammeter will show discharging.
For example, open the door and the dome light goes on. The ammeter will show a a few amps discharge.
Turn the headlights on, and it will show maybe 10-15 amps discharge.
After starting, it should show charging. When the battery is recharged the meter will be centered.
Start and everything goes dead
It sounds like whatever power is available gets diverted to the starter and draws down the battery.
My guess is eventually it recovers a bit.
Stock battery should be a Group 24 (size). Interstate would label it MT-24.
Give a long slow charge if you can.
If you can have the battery load tested that would answer that question.
A handheld voltmeter can be used as a cruder way to check on the car. But it doesn't sound like you have one.
Turn on the headlights. If they are really weak, then the battery is low or the connection is poor.
Start with the connections right at the battery. Each one should be clean and tight. Start with the ground cable and follow it to its other connections. Do not reinstall the connection at the negative post yet. Check the positive cables. The heavy cable goes directly to the starter, the smaller positive cable goes to starter relay. When you're done checking and cleaning the positive cables connections, then reconnect the negative cable to the battery negative post.
