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Thread: Magnetti morelli EFI fault

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    Magnetti morelli EFI fault

    Hi i need a bit of help with my 1999 road king with MM efi had been running fine before an engine re build fired up fine after the re build run it around the block twice felt great on a third test run it had a few splutters and cut out now it won't start it seems to be over fueling it initially starts then cuts out , both plugs very wet and fuel running from the inlet manifold

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    Re: Magnetti morelli EFI fault

    Just borrowed this from another forum, (thanks pa-glazer) this might be a good place to start, are there any error codes showing?

    TROUBLE CODES

    If the Check Engine Lamp stays off for only 4 seconds and then comes back on for an 8 second period, then a functional error is stored (although no current trouble code exists). A functional error indicates an internal problem with the ignition module (trouble codes 52 thru 55) or with the crankshaft or camshaft sensors/timing (trouble code 56).

    If the Check Engine Lamp remains on beyond the 8 second period, then a current trouble code exists.

    Be sure the engine run switch is ON (right handlebar), then turn the ignition switch ON, then off a total of four times, leaving it ON the fourth time. After a two second fast flash of the engine light, there will be an error code of longer flashes, one second each, two second between numbers.

    12 - MAP sensor 44 - bank angle sensor
    16 - battery voltage 52 - RAM ecm failure
    24 - front coil 53 - ROM ecm failure
    25 - rear coil 54 - EEPROM failure
    35 - tachometer 55 - other module failure
    41 - crank pos sensor 56 - cam & crank mismatch (ghost code)
    42 - cam pos sensor

    If turning the ignition on and off four times doesn't activate the diagnostic mode, you can do the same by using a jumper wire in the diagnostic port connector, between the black wire and the light green with red tracer wire. Jump them and then turn on the system, and the codes will flash out. If there is just a really rapid flashing too fast to count, that's the 'intermission', the marker between the repeated sets of codes, and if that's all you get, then there are no codes in the system. The only way to clear the code is to connect the scanylizer or it will clear itself after 50 trips.

    Your problem sounds like a lack of spark, next time it stops, take out a plug and crank over to see if there is anything. The ignition sensor was a weak point on some of these systems and could go faulty when hot.
    Last edited by Simon_A; 23-04-2019 at 09:05 AM.
    Sussex Coaster

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    Re: Magnetti morelli EFI fault

    This is bad news Cha - the MM units are notorious for being unreliable. Even worse is the fact that with them being obsolete most of the parts are unavailable. Just Google 'Harley Marelli problems' and you'll see that there is lots of reading on these. The solution is to bin the lot and replace with a carb but I'm sure that's not what you want to hear at this stage of your build ...

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    Re: Magnetti morelli EFI fault

    Thanks for the info Simon gives me something to work with i had googled the MM system but hadn't foud that one
    Hi Alex the engine ran well too when i started it up , I've had the bike 10 years without a problem did a bit of tuning on it too without a hitch and I've read a few tales of woe abot the MM system hopefully I'll be able to work it out

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    Re: Magnetti morelli EFI fault

    A mate of mine has had his Evo MM Glide about 17 years now all trouble free. I did the heads, fitted a cam and tuned it with a Power Commander III and got 86TQ, 80HP out of it. He must have a good one as it still runs perfectly but there are plenty of horror stories around from not so lucky owners ... Good luck.

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    Re: Magnetti morelli EFI fault

    Thanks Barry tying hard not to go there got a few more options to explore yet

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    Re: Magnetti morelli EFI fault

    The saga continues ��
    Checked what I could with what I could beg borrow and no I haven't stolen anything yet ��
    I've came to the conclusion that my EFI has every thing it needs to fire ie spark fuel compression and it still won't run but as a last gasp I took the cam cover off to check nothing had gone adrift timing wise (cam sensor trigger) so in the last exercise I tried to start it with the headers off and low and behold it did run.
    So now I've put the headers back on it refuses to start

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    Re: Magnetti morelli EFI fault

    Are the exhausts clear?
    Air flow sensor?
    Urrell , Rep Region 23


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    Re: Magnetti morelli EFI fault

    I'm thinking over fuling (flooded)
    Headers removed fresh set of plugs and hay ho it runs
    this is a major breakthrough for me after months of testing and getting nowhere
    It eliminates a lot of stuff
    So not a lot that can cause over fuling Throttle position sensor or perhaps the engine temp sensors????

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