Trying to understand car start process.

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by Kats_Pajamaz, Aug 26, 2023.

  1. Kats_Pajamaz

    Kats_Pajamaz Junior Member

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    I'm not a car expert, but I do most of my own repairs. I feel like I am being hindered with a current repair due to not fully understanding how a prius starts compared to a normal vehicle.

    So in my understanding, in a normal vehicle, you turn the key which turns on your starter, which then proceeds to spin the engine initially. That causes the crankshaft to start rotating, allowing for the normal running of the engine (with sparkplugs, fuel injectors, etc playing their parts).

    1) Is the prius the same way, except it uses the traction battery instead of the starter? Like some sort of linkage that connects to spin the ICE when the traction battery needs charged? Or does it have it's own starter that just runs off of the power from the traction battery instead of the 12v?

    2) If the hybrid system goes to spin the ICE, but the ICE doesn't start, I should be receiving some sort of DTC as to why it isn't starting right? I had a couple buddies telling me that they have car issues all the time that don't generate a code, but I haven't experienced that before and find it hard to believe that a somewhat modern car won't start, but also doesn't have the ability to tell you at least some reason why. I've used a regular plug-in OBD2 reader and also techstream, with no codes pulled from the battery or the ICE.
     
    #1 Kats_Pajamaz, Aug 26, 2023
  2. JC91006

    JC91006 Senior Member

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    Can you give a little history of your car? How it got to the point of it not starting. What did you attempt to change/fix?

    This car just has a lot of electrical bits that can stop you from starting the car, if they are not connected properly. Otherwise, it's very similar to a normal car.
     
    #2 JC91006, Aug 26, 2023
  3. Kats_Pajamaz

    Kats_Pajamaz Junior Member

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    I have a separate thread going about my current fix, I just felt that this might be enough of a different question that it was worth posting by itself. The thread with all of my current problems and peoples help is here Keeps going into Traction battery protection. | PriusChat
     
    #3 Kats_Pajamaz, Aug 26, 2023
  4. Kats_Pajamaz

    Kats_Pajamaz Junior Member

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    Brief summary, I think something is wrong with the ICE, because I can go into READY mode, but when it tries to start the ICE, it will spin for a second then stop. But no trouble codes.
     
    #4 Kats_Pajamaz, Aug 26, 2023
  5. bisco

    bisco cookie crumbler

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    No trouble lights?
     
    #5 bisco, Aug 26, 2023
  6. JC91006

    JC91006 Senior Member

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    Well I can tell you I experienced your problem and it was a dirty throttle body.
     
    #6 JC91006, Aug 26, 2023
  7. bisco

    bisco cookie crumbler

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    So the process goes like this:

    when you step on the brake and press power, the 12 volt fires up the computers and closes the relay to the hybrid battery.
    When the software determines that the engine needs to start, the hybrid battery powers the transaxle to spin the engine.
    Now you’re like a regular car.
    If the engine doesn’t fire, you should get trouble lights, but either way, you need to start looking at fuel, air and spark.
    If you keep trying to start it, you’ll run the hybrid battery down
     
    #7 bisco, Aug 26, 2023
  8. ChapmanF

    ChapmanF Senior Member

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    A starter is an electric motor, so some battery is needed to make it go. You can't have a battery instead of a starter, you have a battery and a starter.

    In the Prius, it just works out that the transaxle already has two big motors inside it. One of them moves the car whenever it turns, so it's not really available for cranking the engine. But the other one is, so when the engine needs to be started, electric power is just sent to that motor, and there you go. There isn't any need to have yet another electric motor bolted on just to be a starter.
     
    #8 ChapmanF, Aug 26, 2023
  9. Mendel Leisk

    Mendel Leisk Senior Member

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    The engine used in the Prius is also used in a gas-only Corolla. There it has a starter motor. For the Prius application the starter motor is deleted, and there's a blanking plate (low on the front/left* corner of the engine) where it would be.

    * "Left" being driver's side
     
    #9 Mendel Leisk, Aug 26, 2023
  10. Tombukt2

    Tombukt2 Senior Member

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    Isn't the reciprocating mass in the Prius always turning whether the engine's firing and actually running and using fuel not necessarily but the pistons are always going up and down? Or is that an earlier generations or something again?
     
    #10 Tombukt2, Aug 26, 2023
  11. bisco

    bisco cookie crumbler

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    The engine turns after a certain mph, depending on the generation
     
    #11 bisco, Aug 26, 2023
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