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Thread: Triumph guys - Detailed technical troubleshooting question

  1. #1
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    Default Triumph guys - Detailed technical troubleshooting question

    1999 Sprint ST 955i. Motor ran but had a knock when I bought it.

    rebuilt motor but it wouldnt start. I removed the gas tank and airbox and performed a spark test with a brand new plug. Cyl3 got 2 really good sparks, tested Cyl2 and got 2 mediocre sparks and then nothing. Cyl1 got nothing at that point. I went back to Cyl3 and got nothing. I am assuming that with the gas tank and airbox removed the bike only carries a residual charge to the coils?

    I replaced the plugs with new, reassembled and it started right up. Ran for 3 minutes, I shut it down to finish reassembling the bike but it wouldnt restart 20 minutes later.

    Cranks over fast and fine but doesnt sound like it is trying to catch at all.
    Any ideas? I know so little about this bike it is difficult to know if I am following the proper diagnostic process.

    I am going under the assumption that this bikes ignition circuit works like many others I have seen. A crank sensor sends signals to the ECU which then grounds out the proper ignition coils in sequence.

    Any ideas? Thoughts? Intelligent responses. Please dont ask me to check a fuse...

  2. #2
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    Im just going to be tossing ideas from thespeedtriple.com

    mixture too rich? swap or clean up the plugs and see if she fires?
    R.I.P. - Reed - 3-23-2008
    Matty V you are missed.

    LRRS/CCS #76 TTD Instructor
    #5/ RSP Racing MTAG Pirelli / StradaFab / / Dyno Solutions / Tony's Track Days /Woodcraft /Armor Bodies /
    MOTUL / Sport Bike Track Gear / Brunetto T-Shirts /



  3. #3
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    call mike weyant, he can fix anything.

    oh...wait...

  4. #4
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    Are the plugs wet (getting fuel)? They should be drenched after a minute of cranking.

  5. #5
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    Unless the tank and airbox have some kind of electrical connection to the coils, i don't see that removing them would have any effect on the ignition system.

    Now that said, the problem as I understand it is the bike starts fine and easy with brand new plugs, the first time, then won't start the second time around.

    First step would be to check the various components of the ignition system (I'm assuming you have a manual, if not let me know and I'll email you one). Check the coils, wires, pickup (if possible) etc. to see if there is a fault somewhere that would cause your spark to weaken like that.

    My next step would be to check the injectors. Unfortunately as I recall the 955 motor has a common fuel rail for the injectors and no retention system so you will have a helluva time checking the spray pattern but you can still clean them and try again. Pull them out, use some test leads to fire them open, then blast them with air or carb cleaner (cover the o-rings so they don't get eaten away). I usually spray injectors from the combustion chamber side to backflush any particles or contaminants, then again from the fuel rail side just for good measure. Reassemble and try again.

  6. #6
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    Quote Originally Posted by Palm Bomb View Post
    call mike weyant, he can fix anything.

    oh...wait...


    Sorry Mike but this makes me laugh, my order is, "shit I'm over my head. call Pilottom. shit, voicemail. Call ducatimike." Keith's idea seems best so far.
    -Gabe, is a racist.

    Matt 9/19/10

  7. #7
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    is the fuel pump priming every time?
    R.I.P. - Reed - 3-23-2008
    Matty V you are missed.

    LRRS/CCS #76 TTD Instructor
    #5/ RSP Racing MTAG Pirelli / StradaFab / / Dyno Solutions / Tony's Track Days /Woodcraft /Armor Bodies /
    MOTUL / Sport Bike Track Gear / Brunetto T-Shirts /



  8. #8
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    Plenty of fuel, possilby too much. Took it apart again, dried plugs which were drenched, reassembled and fired right up. Intermittant miss and then smoothed out. Stopped dead after 5 min of runnning and will not restart. I would bet drenched plugs again.

    This whole thing feels like intermittant spark to me and I am pretty sure its the crankshaft positioning sensor as that is what everything fires off of. Since I had the motor apart I had to mess with it. For all I know it could be dirty on the inside or something. PITA to get to but not all that bad, just need to drain the oil. Getting back on that and will let you all know. Thanks for the input.

    If anyone know of a way to confirm that the crankpos sensor is actually doing its job, I am all ears.

    Also there is a diagnostic connector on this bike which looks just like an OBD-II so I plugged in my really crappy bottom end scanner and it got a few codes but it isnt programmed to speak the trumpets language so I cant really tell. Does anyone know if a regular OBD-II scanner will work with the proper firmware?

    Oh and I appreciate the votes of confidence =). Mechanical absolutely. Electrical/Engine Management becomes far more complex but still not all that bad with the proper tools. The issue is that I dont have the right tools (scanner).
    Last edited by DucatiMichael; 08-01-2011 at 04:36 PM.

  9. #9
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    If you have an obd-II to usb, Tuneboy will have no trouble reading anything. Pretty sure Chris has a copy orrrr you could find it many other ways being a systems admin and all.
    -Gabe, is a racist.

    Matt 9/19/10

  10. #10
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    Quote Originally Posted by drinkingmymilk View Post
    If you have an obd-II to usb, Tuneboy will have no trouble reading anything. Pretty sure Chris has a copy orrrr you could find it many other ways being a systems admin and all.
    Yeah I have just been procrastinating about finding an obd-ii to usb adapter.

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