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Thread: Start and running problem

  1. #1
    apriliaforum newb
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    Start and running problem

    Hello, I am new to the forum and would appreciate any help with my problem.
    My Mp3 400 is a 2008 and has never given me any problems until a couple of days ago.
    It will start right up as it always has but only run for a few seconds and then die!
    Also makes those weird clunking sounds if you try to give it more gas.
    I've replaced the battery, drained the gas and refilled with new gas, checked all
    fuses and yet have yet to find the problem. I no longer ride and need to sell it,
    but can't sell when it won't start up and run as normal.
    Any ideas what the problem might be? Many thanks......

  2. #2
    apriliaforum expert
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    check the seat pressure sensor
    when its stuck it wont detect that you are sitting on it and wont let you rev the engine over 2000 revs
    its located in the front of the seat

  3. #3
    apriliaforum newb
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    Hello Jog, Thanks for responding to my question. Is that switch the one that lights up on dash when you raise the seat?

    If not, I only can locate that one switch which is under the front of the seat.

    If that is the switch you are referring to I guess IT is not stuck because when you raise the seat the dash light comes on and goes off when the seat is closed.

    Am I missing something??? Engine will start but only runs for a couple of seconds and then DIES!

  4. #4
    apriliaforum newb
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    Well, I actually located the seat pressure sensor in the bottom of the front seat.
    How do you check to see if it is stuck?
    If this sensors only function is to limit rpm to 2000 then I don't think that is my problem.
    After engine turns over and runs for only a couple seconds it dies. Will not run for any longer period.
    I can hear the fuel pump run and then stop after a few seconds
    when the key is turned on to the On position.
    Still stumped and ready to pull my hair out!
    Thanks for your idea, any other suggestions that might try to get this running?

  5. #5
    apriliaforum expert
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    it sounds like you have a dirty TPS sensor or a bad crankshaft position sensor

    the bad crankshaft position sensor is easy to diagnose, it will stop sending accurate position of the crankshaft to the ignition system and the spark will dissapear or get into a angle when it cant fire the engine, so when the bike dies pull of the spark plug boot and check for spark if there is none test the sensor resistances with the book to diagnose a fault.
    Also the TPS can get clogged or gum up regulary on the master engine, and will produce a bad idle and often a stall. When the bike is cold it will run because the autochoke program ignores the tps till it warms up but a air leak a dirty throttle flap or gummed up idle channel will stall the engine.

    So happy hunting

  6. #6
    apriliaforum newb
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    Where is the TPS located on the 400 engine?

  7. #7
    apriliaforum expert
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    between the airbox and the intake manifold
    you can access it by removing the underseat storage

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