3 ms·

I have seen similar behavior on vehicles that have a dying alternator. The issue is that one vane of the rotor (or maybe stator?) has shorted and no longer func

I have seen similar behavior on vehicles that have a dying alternator. The issue is that one vane of the rotor (or maybe stator?) has shorted and no longer functions. If when the car is shut off and the rotor stops in a particular position the alternator won’t work. Give it some time and with heating/cooling moving things around just a bit plus the act of repeatedly trying to turn it on potentially making it move just a bit, and it works fine.

addaon 3y ago
Alternators aren't needed for starting. Perhaps a similar issue with the starter motor? But even then you'd hear the thunk of the starter solenoid. Any audible clue definitely makes root-causing simpler.
- bombcar 3y ago
  I have a crank sensor that is going out, and though it still works most of the time if the crankshaft stops in just the right position it becomes an absolute bear to start, and runs in limp mode when it does. Any of the other positions it works just fine.
  - I_Am_Nous 3y ago
    This reminds me of an old F250 my dad had. He towed it from Colorado to Missouri and about halfway he noticed his gas mileage got worse. But, you know, coasting down mountains until you get to plains would also have a similar outcome, so he didn't think about it. Once he got to Missouri he noticed the transfer case (I think) had somehow bounced out of neutral and was partially engaged, which chewed many teeth off the flywheel. To start it we had to get a pipe wrench and manually rotate the flywheel to a spot with enough teeth to catch the starter and turn over. That got harder and harder (as it kept chewing off more teeth) so eventually we had to push start it and pop the clutch. Thankfully it was a manual so it still worked!
    - bombcar 3y ago
      My dad had an old diesel Benz - the generator (that old, didn't have an alternator) went out and for a couple of months we just made sure to park it on a hill and drive during the day. Electricity is overrated!

addaon 3y ago

Alternators aren't needed for starting. Perhaps a similar issue with the starter motor? But even then you'd hear the thunk of the starter solenoid. Any audible clue definitely makes root-causing simpler.

bombcar 3y ago
I have a crank sensor that is going out, and though it still works most of the time if the crankshaft stops in just the right position it becomes an absolute bear to start, and runs in limp mode when it does. Any of the other positions it works just fine.
- I_Am_Nous 3y ago
  This reminds me of an old F250 my dad had. He towed it from Colorado to Missouri and about halfway he noticed his gas mileage got worse. But, you know, coasting down mountains until you get to plains would also have a similar outcome, so he didn't think about it. Once he got to Missouri he noticed the transfer case (I think) had somehow bounced out of neutral and was partially engaged, which chewed many teeth off the flywheel. To start it we had to get a pipe wrench and manually rotate the flywheel to a spot with enough teeth to catch the starter and turn over. That got harder and harder (as it kept chewing off more teeth) so eventually we had to push start it and pop the clutch. Thankfully it was a manual so it still worked!
  - bombcar 3y ago
    My dad had an old diesel Benz - the generator (that old, didn't have an alternator) went out and for a couple of months we just made sure to park it on a hill and drive during the day. Electricity is overrated!