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Thread: Mitsubishi L3E engine noise

  1. #1

    Mitsubishi L3E engine noise

    Apologies for the new thread, but its a different issue

    My L3E is starting a bit better now, but has just developed a nasty 'knocking' type noise.

    Whilst diagnosing I've discovered its something to do with cylinder 2.

    When the engine is started it sometimes sounds fine, all cylinders working, then suddenly a metallic 'knocking' noise starts, almost as if the cylinder is hitting the bottom of the valve.

    I found if I loosen the high pressure fuel pipe to the injector for cylinder 2, the noise stops immediately.

    If I leave it off , the engine runs pretty nicely on 2, accelerating also fine, but as soon as I tighten the fuel up again on cylinder 2, the knocking starts again.

    Has anyone seen anything like this before?

    Can an injector cause this kind of noise ?

    What type of issue could i have that doesnt make a noise whilst running and turning over, until the fuel in the cylinder is turned back on ?

    Cheers...

  2. #2
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    Quote Originally Posted by richp999 View Post
    Apologies for the new thread, but its a different issue

    My L3E is starting a bit better now, but has just developed a nasty 'knocking' type noise.

    Whilst diagnosing I've discovered its something to do with cylinder 2.

    When the engine is started it sometimes sounds fine, all cylinders working, then suddenly a metallic 'knocking' noise starts, almost as if the cylinder is hitting the bottom of the valve.

    I found if I loosen the high pressure fuel pipe to the injector for cylinder 2, the noise stops immediately.

    If I leave it off , the engine runs pretty nicely on 2, accelerating also fine, but as soon as I tighten the fuel up again on cylinder 2, the knocking starts again.

    Has anyone seen anything like this before?

    Can an injector cause this kind of noise ?

    What type of issue could i have that doesnt make a noise whilst running and turning over, until the fuel in the cylinder is turned back on ?

    Cheers...
    Hi,

    I have the same L3e engine with some 3500hours on it. It has the knocking sound as well. I have adjusted the valves and that might have changed the sound a bit, but it still knocks. Injectors are a good suspect as the cause all kinds of funny things when not working properly.

    Havenít asked for an offer on adjusting the injectors as the engine runs quite ok.

    Maybe Muz, the wizard of -15Bís know a bit more about the knocking?

    Br.

    matt

  3. #3
    Quote Originally Posted by Mattir View Post
    Hi,

    I have the same L3e engine with some 3500hours on it. It has the knocking sound as well. I have adjusted the valves and that might have changed the sound a bit, but it still knocks. Injectors are a good suspect as the cause all kinds of funny things when not working properly.

    Havenít asked for an offer on adjusting the injectors as the engine runs quite ok.

    Maybe Muz, the wizard of -15Bís know a bit more about the knocking?

    Br.

    matt


    Hmm yeah I suppose I could try swapping injectors 1 & 2, and see if that makes any difference.

    New injector isn't too expensive a fix, if thats what it is.. I have tested them all though and it seemed to be performing ok on the injector tester..

    The sound is a bit too loud - but as you say it could be injector causing something else .. Maybe dribbling fuel out before its supposed to, and that fuel is igniting early causing knocking ?

    I'll swap with the one of the cylinders with no problem and see what happens..

    My big worry is that its something more serious.. but then when the fuel is cut off to it, theres no knocking at all ...

    Could say a piston / rod etc sound fine until the pressure is put on it (fuel going in )??

  4. #4
    Admin Muz's Avatar
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    Many of them knock when cold.. but that gradually dissapears as they warm .. cracking an injector just alters the crank speed and 'appears' to change the knock.. these seem pretty good engines in general .. only get problems when thrown over on their sides in diggers , and left to run
    Please don't PM me for plant advice.. thanks .. Post in the forum where I will gladly help, as will many of our contributors.. as the info and responses will help everyone else, which is why we exist

  5. #5
    Quote Originally Posted by Muz View Post
    Many of them knock when cold.. but that gradually dissapears as they warm .. cracking an injector just alters the crank speed and 'appears' to change the knock
    I'll get a video of it tomorrow.. It's very odd.. If I crack the injector, the noise stops. If I then increase the revs, the noise stays gone , it doesn't seem to come back when the revs go up. It actually sounds pretty good on those 2 cylinders!

    I might have a video of the noise on my phone now, ill have a look.. But I'll video the injector being cracked off tomorrow..

    Its a really different, metallic sound ; as if something snapped or broke inside the cylinder. But then if it stops when the fuel's cut, surely that rules out anything major cracked/broken off etc..??

  6. #6
    Admin Muz's Avatar
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    If its in a digger maybe its run a big end cos it was tipped .. but that would be either No 1 or 3 .. hard to tell that until you take the sump pan off and will see the metal blue in colour on those bearings because of the heat they've had
    Please don't PM me for plant advice.. thanks .. Post in the forum where I will gladly help, as will many of our contributors.. as the info and responses will help everyone else, which is why we exist

  7. #7
    Quote Originally Posted by Muz View Post
    If its in a digger maybe its run a big end cos it was tipped .. but that would be either No 1 or 3 .. hard to tell that until you take the sump pan off and will see the metal blue in colour on those bearings because of the heat they've had
    I'll check if i take the sump off again.

    I did have the engine out 2 years ago, and change all piston rings etc... didnt notice anything then..

    Anyway heres the current video, I'll do a better one tommorrow


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    Quote Originally Posted by richp999 View Post
    I'll check if i take the sump off again.

    I did have the engine out 2 years ago, and change all piston rings etc... didnt notice anything then..

    Anyway heres the current video, I'll do a better one tommorrow

    the video asks for permission. Canít be viewed.

  9. #9
    Ah Damn.. I'll sort it later, I'll get a better video of the injector being turned off...

    Edit:

    Sorted, should be able to view now

  10. #10
    Admin Muz's Avatar
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    yeah sounds like a valve set incorrectly or a big end shell
    Please don't PM me for plant advice.. thanks .. Post in the forum where I will gladly help, as will many of our contributors.. as the info and responses will help everyone else, which is why we exist

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