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  • Engine dies

    Hello all I have a problem.
    my engine 5.0 mpi mercruiser seems to start and run great first half hour or so then just dies. Wait 20 seconds and it will start right up idle fine and run fine in gear but as soon as I try plain off it shuts off again. Any ideas thanks

  • #2
    Have a motor serial number?
    Does it shut down like turning the key off or bog down and stop?
    94 Formula 27PC Custom 509MPI MEFI3 , B3 XR
    95 Rinker 232 w/ 7.4L Carb 0F425011 B1 0F486471
    07 Seadoo GTX
    Merc Adults Only VP Adults Only
    G-Dad always said "First Liar doesn't stand a chance"

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    • #3
      Motor serial # 0M693783
      motor shuts off as if turn key off no bogging down or anything

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      • #4
        When it shuts off do you hear any beeps?
        When restarting does the key get turned OFF then back ON or can you just turn the key to start?
        Does the voltmeter show more then 12V when running?

        I'm wondering if its loosing power because the main power relay opens and then closes in a few seconds. It does sound like an electrical issue, and something is heating up because of running fine for first half hour
        94 Formula 27PC Custom 509MPI MEFI3 , B3 XR
        95 Rinker 232 w/ 7.4L Carb 0F425011 B1 0F486471
        07 Seadoo GTX
        Merc Adults Only VP Adults Only
        G-Dad always said "First Liar doesn't stand a chance"

        Comment


        • #5
          The volt meter shows 14 .5 It doesn’t beep when shuts down but when turn key off and on it beeps once but starts right up with no issue or other beeps. I do have to wait several seconds 20 maybe before starting or it just turns over.

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          • #6
            If you turn key off and back on right away, and it just cranks but no start, does it beep once?
            Or only if you wait 20 seconds?

            Also do you hear the fuel pump run for a moment on both on/of or wait 20 seconds?
            94 Formula 27PC Custom 509MPI MEFI3 , B3 XR
            95 Rinker 232 w/ 7.4L Carb 0F425011 B1 0F486471
            07 Seadoo GTX
            Merc Adults Only VP Adults Only
            G-Dad always said "First Liar doesn't stand a chance"

            Comment


            • #7
              It beeps once every time turn key on I believe. The fuel pump kicks in for few seconds when turn key.

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              • #8
                Originally posted by Noris View Post
                It beeps once every time turn key on I believe. The fuel pump kicks in for few seconds when turn key.
                Was hoping it wouldn't beep when it didn't start because it might be the main power relay (MPR). If the relay didn't energize then there would be no beep but it would crank and not start. Your motor has 2 relays which are next to each other (MPR and Fuel pump) and they are the same and can be swapped. Try swapping them just for just to see if things change

                Try to start without waiting the 20 seconds and look for the tachometer and see if it shows 300 or so rpms when cranking. If no rpms is showing then might be the crankshaft position sensor.

                Going to need to check for 12V at the coil, and issue will be is we only have 20 seconds. These motors have a flat distributor cap and have a long history of failing without warning, but most times they just start missing. Most replace the cap and rotor as a preemptive measure and if that didn't fix the issue, keep the old on board when it actually fails for real.

                Connect a voltmeter or test light to the pink/white wire on the coil, hope we can see if power is lost. Something that would kill the motor is the kill switch (man overboard). Could jump across (bypass) to see if this is causing the loss power
                94 Formula 27PC Custom 509MPI MEFI3 , B3 XR
                95 Rinker 232 w/ 7.4L Carb 0F425011 B1 0F486471
                07 Seadoo GTX
                Merc Adults Only VP Adults Only
                G-Dad always said "First Liar doesn't stand a chance"

                Comment


                • #9
                  Sign up today
                  I did bypass the kill switch no help but I will check the rest tonight or tomorrow and keep u posted. Thank you for all your help

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