Why does my starter engage for only a second, then spin freely after that. it was removed and tested at Autozone and passed. The starter stayed engaged during the test when no load was encountered.
Hi Anonymous
What I believe you've said is that you turn the key to start, the engine turns over for a second, then you just hear the starter spinning but no engine turn over. Yes?
Then you took it to Autozone and tested it and it stayed engaged during the test. The differences, possible or real here, are the load on the starter gear end, and the electricity driving it.
There are a couple things happening in the start cycle. The motor starts spinning and the solenoid pushes the spinning gear forward to engage the toothed edge of the flywheel. If the solenoid doesn't push enough, the gear won't engage. So, one thought is that there's an issue with the solenoid - it may push the gear out just fine, but lack power to keep it pressed forward if there is back-force from the engine.
If you have a poor connection to the battery, the solenoid may not draw the current to keep the gear engaged. Checking the hot (red) wire both at the battery and where it attaches to the starter is the primary diagnostic there. Even if the battery has a good charge, the current draw if starting is the heaviest load it encounters in a typical day of driving, so the ability of the battery to dump that charge quickly in a pulse of high current is also important, and non-corroded, tightly connected wires help.
The starter gear also has a clutch in it - akin to the freewheel on the rear of a bike, or a ratchet. This lets the gear spin faster than the starter motor once the engine catches, so that the engine doesn't essentially grab the engaged starter motor and spin it waaay too fast. letting back on the key lets the fast spinning gear disengage without trouble. If there is an issue with that clutch/ratchet, that might also be allowing the gear to spin without it actually pushing - like the clicker in a ratchet sticking so that it'll spin either way.
After that.... there is likely both a relay and a fuse for the starter. Not a bad idea to check that neither is blown, or, in the case of the relay, looking sort of browned and cooked.
Hope this helps!
D
