96 Blazer sporadic cranking issue

I have 96 Blazer 4.3L. Every 6-10 tries the engine will not crank. The rest of the time it is fine. When the issue occurs, the truck will not start for approx 20 tries or 3-4 hrs and then for no reason it will crank again.
The dash lights dim and the fuel pump runs.

I have replaced the starter, but same issue.....

Starter relay? (If so, where is it?)

Help!

so it will turn over and rotate but not start up?

Or will it not even turn over?

When it happens, not even turn over......

Then it will be OK for a few days. I can not determine a pattern.

Check you battery.

Take a voltmeter out and check the voltage with the truck off and come back and tell us.

The battery stays at about 12.8 V.
When the issue occurs , the truck may crank again as quick as within 2 or three tries. When it does crank over it is fine.

Take the battery out and charge it for a couple of hours at 10 amps.

Sounds like you battery is on its way out.

How old is it?

About 1 year.
When it doesn't crank there is nothing...when it does, then it cranks at full speed. I would expect a bad battery to be a little more consistent than this?

Check all your connections going to the starter for tightness and cleanliness.

This just happened to our 97 Blazer. Problem is once it died, it did not start again. Had to be towed. It was the ignition switch. Never would have suspected that one.