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  1. #1

    MSX 110 High Temp warning limp mode

    Hi guys,
    I am in this way too deep to quit now. I need some more Greenhulk great advice. When I purchased this MSX 110 I was told the only thing wrong with it was a bad oil cooler “not too expensive to fix”. So far this is what I have done:
    The nikasil had flaked off the head 70 psi on front piston so I had the block bored renikasiled and honed. New pistons, new oil cooler, new oil tank with role over tank, new water pump, new thermostat and the list goes on for a long time. I think I paid for Randy’s vacation this year.

    So finally I have the engine back in for the 3
    rd time and I’m getting a High temp warning almost instantly with the engine in limp mode 1800 rpms, with no throttle. Is it possible for the computer to be stuck if so is there a way to unstick it. I live near Allentown Pa and I can’t find anyone within 200 miles to look at it. Any advise it always greatly appreciated.

    Thanks Tim
    Last edited by K447; 03-05-2013 at 10:37 PM.

  2. #2
    ripcuda's Avatar
    Join Date
    May 2010
    Newman Lake, WA
    Hi Tim...

    Here's what the service manual says about ECU rev limiting
    RPM Limiting Modes
    The engine management software will limit engine RPM in several different scenarios. Engine RPM is limited
    to protect either the operator or engine from injury of damage.
    RPM will be limited when the following occurs:

    Idle RPM............................1550±50............ ..Normal Operation
    Maximum Engine RPM............7800--8400.........Rev Limiter Function
    Limp--Home Mode................1750...................Failure with either the ECU, ETB, or PPU components.
    Reverse Mode......................3400..................Op erator moves reverse handle from forward position to either neutral or reverse positions.
    Overboost Mode*.................4700--4800.........110: Boost exceeded .8 -- .9 BAR for more than 400ms. 150: Boost exceeded 1.3 BAR for more than 400ms.
    Engine Overheat*.................1600--1800.........The engine coolant temperature exceeds safe operating range.
    Exhaust Manifold Overheat......1800..................The exhaust manifold freshwater cooling temperature exceeds safe operating range.

    * = Indicates a TORQUE REDUCTION running mode. The ECU limits engine RPM by limiting the amount of
    torque generated by the engine. Stated RPM limit is an approximation and changes with current engine operating

    The throttle plate opening (aperture), ignition timing, and fuel supply are controlled by the ECU to limit engine RPM
    in all modes except in the LIMP--HOME MODE.

    Ignition timing is gradually retarded as the engine RPM reaches the established RPM limiter specification. If RPM
    exceeds 7600 RPM, ignition timing is retarded and fuel supply to one or both cylinders is reduced.

    The limp--homemode occurs whenever a problem is detected as a safety issue in the Electronic Throttle Circuit.
    The ECU will cut power to the ETB in the event of a PPU, TPS, or wiring failure. When in the limp--home mode,
    the throttle plate returns to it default, non--power position. This position represents 6% open or approximately
    1750 RPM.

    Cold--Start Protection
    The ECU will limit engine RPM to idle speed during a cold startup. Full power will return when the engine coolant
    temperature exceeds 140_F (60_C). The cold--start protection will last approximately 30 seconds after initial
    startup depending on current conditions.
    So... could be a couple things limiting you to around 1800 rpms. First, you're getting a High Temp warning... so start there. There are two temp sensors. The main coolant sensor between the intake manifold runners on the coolant rail... and the exhaust temperature switch (not really a sensor)... on the rear side of the exhaust manifold... single wire push-on connector. Start with the exhaust temp switch and unplug it. Unplugged... the ECU thinks that switch is not tripped (overheated) and you loose any sort of overheat protection on the exhaust... but it's an easy way to see if this switch is bad. After that... check your coolant sensor and wiring connector.

    Other than those... you can also see an ECU / ETB / PPU failure would cause a similar RPM limit and no throttle. Check all your connectors for those.

    As for ECU stored codes and such. I've read multiple folks saying it took a ECU reflash to cure their ECU troubles (whatever they happened to be)... I seem to recall they were usually rollover related and not running right even after cleaning/fixing. So it's possible. Desperado (Martin at Precision Sports) is the ECU guru. I've read this replies about how the ECU stores the codes in current... then after so many on/off cycles without further problems... the codes go into a history setting of some sort. Sorry, but I've never had ECU problems. Before I even got my MSX in the water... I had sent my ECU to Martin for a Staged upgrade reflash which wiped it clean.


  3. #3
    I pulled the exhaust temp switch this does away with the temp warnig light and limp mode, my problem now is I cant get the engine to Idle. As soon as I take jet out of reverse the engine starts to scream. I still don't know it the throttle is working yet because I don't want a fresh rebuilt to get destroyed. Will the engine idle normal on a hose? What should I try next? I have a new exhayst temo switch that should be here on Fri.
    Again any help is appreciated.
    Thanks Tim

  4. #4
    Click avatar for tech links/info, donation request K447's Avatar
    Join Date
    Jul 2007
    near Toronto, Canada
    Sometimes the Weber engines will not idle without a water load on the impeller. The engine can decide it wants to rev up when on the garden hose, which is why it is recommended to always have it in RPM limited Reverse mode when running out of the water.

    Put the hull in the water and the idle should settle down.
    Last edited by K447; 03-11-2013 at 10:29 AM.

  5. #5
    ripcuda's Avatar
    Join Date
    May 2010
    Newman Lake, WA
    When I start my engine on the hose... in reverse... the idle is steady and I can tap the throttle and it will go up just a little to the 3400 rpm (reverse engaged) limit. When I disengaged reverse, it will still idle fine as long as I didn't touch the throttle. If I try to blip the throttle... it will go sky high like you describe.

    I've never had idle issues in the water. Revs have never went sky high (like on the trailer) in the water. It has always behaved perfectly as expected in the water.

    P.S. I have a clean, trouble-code-free, Precision Sports Stage2 reflashed ECU.


  6. #6

    Join Date
    Oct 2011
    It's fairly normal for the "free-rev" to occur with no load on the jet-pump.
    I'm not 100% sure, but often you will experience this more frequently after a component failure or disconnecting the battery, etc. The ECU possibly relearns the low speed throttle positions, as the ecu really doesnt have the function to monitor fuel when there isnt a load on the engine. (see the adaptive fuel relearning mode).
    I wouldn't stress out about it until you water test it. There is a lot to be learned from the notes on the adapative mode relearning process, and I know the info is on the site somewhere.

    Try this, just for fun...
    Disconnect your water temp sensor from the wiring harness, and make a jumper wire from the sensor to ground. This should accomplish the same thing as putting it in reverse.


  7. #7
    It's been a while since I've posted anythig so here is an update. The oil and water are in great shape, no more antifreeze in the oil. I believe on of the issues was me not following proper protocal on torqueing the head down. Once I torqued the head down I never followed up on the 180 degree turn (huge difference). I still get the free rev when the ski is not in reverse so I guess I'll have to wait a couple more weeks to get it in the water to see what happens. Again thanks for all the help. If most of you didn't live a 1000 mile away I'd buy ya a beer.
    Thanks Tim

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