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  1. #1

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    TPS-what is the expected voltage?

    Hi there,
    my MSX 140 couldn't reach top speed, the top in my last drive was 70km/h.
    i have measured the TPS voltage and it was 3.7volt WOT.
    i have found out that the mechanical connections between the air valves (the main axis of the air intake is built from 3 small axis connected by brass connections) are a bit free. After fixing them it improves the axis stiffness and the TPS shows now 4.3volt in WOT.
    is this normal or should be 4.7v as in the manual?

    Gabi


  2. #2
    Click avatar for tech links/info, donation request K447's Avatar
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    I will check my notes regarding TPS voltages and reply later.

    Mechanically, are all three throttle body valves closing and opening together? When one air valve throttle plate first touches fully closed while very slowly releasing the throttle lever, are the other two throttle plates also just touching at the same time?

    It is important that all three throttle plates be synchronized so they touch closed at the same time.

    When slowly squeezing the throttle from idle (throttle cable slack) all three air valve discs must begin moving open at the same time.

  3. #3

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    Quote Originally Posted by K447 View Post
    I will check my notes regarding TPS voltages and reply later.

    Mechanically, are all three throttle body valves closing and opening together? When one air valve throttle plate first touches fully closed while very slowly releasing the throttle lever, are the other two throttle plates also just touching at the same time?

    It is important that all three throttle plates be synchronized so they touch closed at the same time.

    When slowly squeezing the throttle from idle (throttle cable slack) all three air valve discs must begin moving open at the same time.
    There was a bit diference between them (a milimeter or two) so i removed the intake and fixed it. Now all move togeter. And the TPS voltage increased from 3.7v to 4.3v in WOT.
    I have 2 TPSs, both work the same.
    Gabi

  4. #4

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    K447,
    i just back from the sea, she's running like a crazy.
    Speed 99km/h
    but anyway, if you have the information whats the expected TPS voltage in WOT, i' would be happy to know.
    Thanks,
    Gabi

  5. #5
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by Gmagnezi View Post
    K447,
    i just back from the sea, she's running like a crazy.
    Speed 99km/h
    but anyway, if you have the information whats the expected TPS voltage in WOT, i' would be happy to know.
    Thanks,
    Gabi
    I do not have all my notes at hand, but the actual voltage measured on my TPS is very close to 4.70 volts. The exact voltage produced by the TPS at maximum throttle varies depending on the TPS and the mechanical 'slop' at each joint in the throttle shaft linkage. A voltage of 4.6x volts would be 'close enough' in my opinion.

    Tip: Loosen the TPS bolts just enough to allow you to twist the TPS body against the TPS mounting bolt sides. Turn the TPS so the output voltage at idle is maximum. Tighten the TPS bolts while holding the TPS at maximum idle voltage. Do not over tighten the TPS bolts.

    Note: TPS voltage at idle position is often circa 0.42 to 0.5x volts depending on the TPS and the installation.
    Official specification is 0.350 volts, going from memory.

    Tip: Set the slack in the throttle cable to just barely allow the throttle plates to rest closed. There should be only a tiny amount of slack in the throttle cable from the finger lever. Make sure the throttle plates are fully closed and they do not move when you turn the steering left and right.

    Test: When the throttle lever is tightly squeezed by hand, press on the actual exposed throttle cable. Watch the throttle plates while you press on the exposed cable.

    The throttle plates should already be fully open and should NOT move any more when you press against the side of the exposed cable at the finger lever.

    Tip: If you use the Ficht EMM Service Power jumper (jumper wire in the 8-pin wire harness connector) you can measure and set the TPS voltage with the engine not running.
    Last edited by K447; 04-18-2014 at 02:40 PM. Reason: 0.350 volts spec

  6. #6

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    Great Tips K447
    i'll use them to improve the mechanizm that is driving the TPS to get a closer voltage to 4.6v and up.
    I'll keep update if i'll succeed.
    Thanks a lot

    Gabi

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    This is what apears in the maintenance guide page 4.6:
    "THROTTLE POSITION SENSOR(TPS DATA CAN BE VIEWED USING PODIAG / ENGINE MONITOR- ING FUNCTION.). 4.70 VDC +/- 05 VDC @ 85 THROTTLE OPENING (USE THROTTLE FLIPPER) APPROXIMATELY .350 VDC CLOSED.

    Gabi

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    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by Gmagnezi View Post
    This is what apears in the maintenance guide page 4.6:
    "THROTTLE POSITION SENSOR(TPS DATA CAN BE VIEWED USING PODIAG / ENGINE MONITOR- ING FUNCTION.). 4.70 VDC +/- 05 VDC @ 85 THROTTLE OPENING (USE THROTTLE FLIPPER) APPROXIMATELY .350 VDC CLOSED.

    Gabi
    I suspect the 85 throttle opening is misunderstood.

    The throttle plates go from vertical open to fully closed, but the total included angle of rotation is less than 90 degrees. The throttle plates are not perfectly horizontal when the throttle is fully closed. I have not actually measured it, but I expect the total angle of rotation of the throttle shaft is about 85 degrees, fully closed to fully open.

    Going from memory, 0.350 volts is perfect for TPS idle position. Sometimes a TPS will not quite get to 0.350 volts at idle. What is important is that the TPS voltages be close to correct at BOTH idle and at wide open throttle.

    I think the EMM has some ability to compensate for slightly incorrect idle TPS voltages. So if you start the engine and the TPS says 0.45 volts and is stable at idle, the EMM will self calibrate and accept 0.450 volts as 'idle'.

    At wide open throttle the EMM does not self-calibrate, as far as I know. The EMM just looks at the actual voltage coming from the TPS relative to 4.70 volt specification for wide open.

  9. #9
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    Which wire from the TPS are you measuring this voltage on?

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    Quote Originally Posted by BryanP View Post
    Which wire from the TPS are you measuring this voltage on?
    TPS has three wires from the wire harness.

    Black wire at the TPS connector (one side of the three pin connector) is the TPS circuit ground, which is your reference point for your black multimeter probe.

    Note: If you connect the black meter probe elsewhere (such as engine ground or battery negative post) you may get misleading readings as the voltages around the TPS are fairly precise. A few tenths of a volt can make a difference.

    At the far side of the TPS connector (opposite the black wire) is the power feed pin. This is 5 volts when the EMM is awake. When the engine is not running and the EMM is sleeping there will be no useful voltages at the TPS.

    The center pin in the TPS connector is the TPS signal voltage pin. Red meter probe on this pin monitors the throttle position signal (DC volts) sent from the TPS back to the EMM.

    At idle the TPS output voltage specification is 0.350 volts, or quite close to that.

    At wide open throttle the TPS output voltage should be 4.70 volts or very close.

    Note: The EMM has a special regulated 5 volt power feed for the TPS. This is isolated from the main power circuits in the watercraft. Do not jumper 12 volt battery power to the TPS.

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