Starting issue

The smaller the wire #, say 10 gauge vs 14 gauge, the larger the wire. A larger wire that is good should have less resistance than a smaller one and therefore less voltage drop. Can't just look at cables even though good to do a visual on connections. Cables/wiring can become internally corroded or black and not carry what they need to do their job. You can remove both ends (at starter and at battery) of the positive cable and check the resistance (ohms). Do the same for the negative. Clean the ground connection at the frame and also do a voltage drop test on it. Good then to coat with silicone dielectric grease. Voltage drop can be done between any 2 points so if a large drop is found then you can go between one end and a closer connection to isolate the problem. Plenty of videos on you tube for checking a starter circuit. Ford Tech Makuloco has a really good video on this and the principles apply to any starter circuit.

 

If I read OP correct. It only cranks by hitting the starter with power. Check the starter relay solenoid ( whatever it’s called) Check the wires running in and out of it. Very common for them to break. It’s located on firewall near foot brake valve and wiper motor.

 

I wouldn't rely on checking ohms of a wire. Been burnt on that in the past.

 

Put the other one from Battery positive to starter positive see what happens.

 

Key and button works? If so forget about the relay mentioned.