Only starts with a jump

Welcome to 2CarPros.

When you try starting it without the jump, what happens? Does the starter engage and turn the engine or does nothing happen.

I have to be honest, since it works with a jump, it should work without if the battery is good. Since you confirmed the battery is good, then I suspect there is a loose terminal or issue with a connection at the battery or the main wires from the battery.

What I have seen happen is this. When the jumper cables are attached, the tension from them forces a connection with the battery and the starter engages. When they are removed, corrosion or a loose terminal no longer makes a good connection and the starter won't engage.

Even though you are jump starting the vehicle, only 12v exists to the starter. It isn't like the voltage is doubled. So, that is why I feel it is a connection issue.

Here is a link that explains how to check and service the terminals. It title indicates that everything goes out when you try to start the engine. However, I need you to follow the procedures for cleaning and inspecting the terminals. Additionally, confirm that the ground to the engine block is clean and tight.

https://www.2carpros.com/articles/everything-goes-dead-when-engine-is-cranked

Let me know what you find. Also, please feel free to ask questions if you have them.

Take care,
Joe