I am not a mechanic but have dealt with old cars most of my life. It has been my experience that a starter does not just die right away. It "drags" or does not have that clean, robust spinning sound you associate with a car which starts normally, say within 3 seconds after you turn the key. In the past I have found usually it is the starter bendix or the starter solonoid. From my understanding, the bendix is a gear like device which enables the starter to engage the engine. The solonoid is like a switch that turns on the starting equipment. There are so many things that can go wrong with a car electrical system that I suggest you find a really GOOD starter shop. Too many times even competent mechanics use trial and error and you really need some theoretical understandng of electronics to make a proper diagnosis. Geoff
You know the starter is going bad when you have a dragging starter.
Remove the starter and have it bench tested.
Remove starter and bench test it for operation and current draw
You need to remove the starter and look at the teeth on both parts.
Remove the battery and take it to an auto parts store for testing. They can tell you if it is bad. If it is good, then remove the starter and do the same thing.
If the starter does not turn then it could either be bad or not getting power. If a volt meter can not be used to determine that voltage is present, then the starter can be pulled and taken to be tested.
Remove it and have it bench tested.
jump the starter solnoid, if it will crank , turn key on and jump again, if it starts then key switch is ok it would be the starter solnoid that's bad,
If a starter relay or solenoid is bad, usually you will only hear a single click when you turn the key to start the engine.
Remove the starter and inspect the ring gear on the flywheel.
Good power all the way to the starter, 12 volts at solenoid/start circuit wire when key engaged, but no click or starter engage
First, turn on the headlights. Now, have someone watch them as you try to start the car; do they get dim? If so, the battery is in need of a charge; If not, you need to check your connections at the starter. You may have a bad starter, starter solenoid, or connection.