Starter Ignition Neutral switch
Starter solenoid.
Never disconnect a battery while an engine is running!
may be on top of the starter and replaced with same. Follow the + battery cable it will connect to the solenoid
the starter solenoid only engages the starter when the key switch is activated. the alternator is what charges the battery which is located under or along side the flywheel
The wire from the battery to solenoid is corroded & should be replaced.
Check the battery cables or starter.
Starter problems can be caused by several things: Weak battery because of battery failure or alternator that is not charging the battery. Falty connection between the battery and the starter. Solenoid failure or bad connection on the solenoid. Starter failure. Neutral lockout switch failure. Bad connection between keyswitch and starter.
Voltage Regulator?
You should locate and test the solenoid. Most have three connections. There is a large cable from the battery to the solenoid, from the solenoid to the starter and from the start switch to the solenoid. The power terminals to the battery and the starter are large and have large cables. The starter switch connection is much smaller. Turning the key to 'start' provides a low current voltage to the solenoid causing the solenoid relay to close and power from the battery cable to connect through to the starter. If that voltage is present then the solenoid or the wiring between the solenoid and battery or solenoid and starter is suspect. If that voltage is missing then the starter switch or solenoid feed line may have failed.
You need to replaced the starter or the alternator.
Dead battery? Loose or dirty battery cables? Bad starter solenoid? Bad starter? Neutral switch?
Solenoid or battery *Check the alternator as well. When my Camry did that, the battery and alternator both needed replacement. -andey78