No starter? The engine wont crank over?

Sounds like a typical bad battery cable connection. The GM side terminal battery design lets the acid creep into the connector and down into the wire itself. From the outside the connector looks fine, but under the rubber coating it is actually eroded away. It can happen on either connector. The other area to check is that the grounds are all good. The ground at the back of the right head likes to rot off and you lose the body to block ground path. It sounds like the battery is weak or the starter has gone out but to be sure lets check out these guides, they can help us fix it

https://www.2carpros.com/articles/starter-not-working-repair

and

https://www.2carpros.com/articles/car-battery-load-test

Please run down these guides and report back.

I would suspect the starter motor. cranking a engine over for extended periods of time with a weak battery melts the brushes in the starter motor. your battery may have been your initial problem but in turn you cooked your starter motor. This guide can help us fix it

https://www.2carpros.com/articles/starter-not-working-repair

Please run down this guide and report back.

Have a helper turn the key to the start position while you check for voltage to the smaller wire on the starter. You should be getting 12+ volts. Let me know what you find.

Hey Be,
There is a oil pressure safety, but it won't prevent it from turning over. It only shuts the engine down while its running (if there is an oil pressure problem) Some quick things you can check. Battery cables, for corrosion and tightness. Battery, for the proper charge. If all that is well, then it sounds like your starter has failed and needs to be replaced. Let us know!

Chris

I just fully charged both batteries and when I turn the key, it barely turns over. If you meant the starter motor cranks the engine slowly and just goes dead from there-could be the starter motor overrunning clutch is slipping or you have a bad ignition switch to include the starter relay-check this 1st

Test the battery with a voltage tester. Check and clean up the battery terminals. Make sure all of the connections are clean and tight.
When the engine cranks - and the fuel pump is working - it is likely that fuel is getting into the cylinders. If it is, and if that fuel does not fire - it will just keep pouring in - this will cause your engine to become bound up with raw fuel. Liquid does not compress - the more liquid (gas) that gets into the combustion chamber the harder the engine will crank - until eventually the engine will become hydraulicly bound up. This could bend push rods or worse. Remove all of the spark plugs and check and see if they are wet with fuel. If they are then there is no spark. Also, if the spark plugs are wet, then there is raw fuel in the combustion chamber. To remove this fuel - remove the fuel pump relay (located in the fuse block under the hood) and crank the engine for a few seconds (without the spark plugs installed).
If no spark -Make sure all of the fuses are good. Then test the ignition control module and the coil. Autozone or a place like that can test this for free.

Is it the original starter? If so, the Bendix fork or bearing is worn. Replace the starter. If it is a newer starter, it is out of alignment and you need to install some shims so it is not binding.

Did this happen with the old starter too? If not, why was the starter replaced? Do you hear anything when you turn the ignition switch to "crank"? You might hear the rather loud clunk of the starter solenoid. Also listen closely for the fairly light click of the starter relay. If you don't hear either of those, the neutral safety switch becomes a good suspect. Try shifting in and out of "park" a few times, then try cranking the engine.

Next, start by checking fuse 8 in the instrument panel fuse box. If that is okay, the starter system can be broken down into four parts, each with a test point at the starter relay's socket. You'll need a test light, but be careful to not poke it into the terminals too hard as that can stretch those terminals and cause an intermittent connection later. If you need it, here's a link to an article on using a test light:

https://www.2carpros.com/articles/how-to-use-a-test-light-circuit-tester

Let me know what you find up to this point.