Mitsubishi L3E engine noise

[richp999]

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...

[Mattir]

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.

Haven’t asked for an offer on adjusting the injectors as the engine runs quite ok.

Maybe Muz, the wizard of -15B’s know a bit more about the knocking?

Br.

matt

[richp999]

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.

Haven’t asked for an offer on adjusting the injectors as the engine runs quite ok.

Maybe Muz, the wizard of -15B’s 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 )??

[Muz]

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

[richp999]

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..??

[Muz]

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

[richp999]

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

[Mattir]

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. Can’t be viewed.

[richp999]

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

[Muz]

yeah sounds like a valve set incorrectly or a big end shell

[richp999]

yeah sounds like a valve set incorrectly or a big end shell

Hope its the valve...

How would the valve but incorrectly set to make this noise ? I mean I'll check it out, what should I be looking for ? Too loose, or too tight ?

Also by 'big end shell' do you mean the shell bearing that goes between the rod and the crankshaft, or the crankshaft and the engine block ?

If I remember I should be able to change the bearing on the rod/crankshaft by just taking the sump off, might not have to remove whole engine...

If I take the sump off, should I be able to 'feel' movement between the con rod and crankshaft if its gone, or will it still be tight, just still too worn and I need to take it off to look at ?


Cheers

[Muz]

If a valve is set incorrectly it may hit the piston, or if the shaft has sheared it may be loose. If its been tipped .. it might have run a big end as I said earlier .. so the crank picks up metal from the bearing shell and wears both giving the ticking noise which varies with revs.. like I said, this will be obvious by the colour of the metal when you see it

[Mattir]

Viewed the video. The engine sounds a lot different than mind. There’s a clear metal sound. I quess you start with the valve clearings. They are rather easy to set. 0.25mm inlet and exhaust, adjusted with cold engine.

My -15b does sound at all the metallic but rather like beating a kettledrum. It’s hard to explain,but even though it runs nicely, there might be an issue with one of the cylinders.

[richp999]

So, video of the injector being loosened..

So going to:

1) Check valve & setting clearence.

2) Swap injector over just incase its something to do with that.

3) After that the only thing that should be left is a problem with piston/rod/rod shell bearing , so i'll take sump off and check.

Only in that order because its the easiest to do :)

I'll try that today and see where I get up to.

[Mattir]

So, video of the injector being loosened..

So going to:

1) Check valve & setting clearence.

2) Swap injector over just incase its something to do with that.

3) After that the only thing that should be left is a problem with piston/rod/rod shell bearing , so i'll take sump off and check.

Only in that order because its the easiest to do :)

I'll try that today and see where I get up to.

nice video, thanks for posting.

As the metallic noise reappears on idle, I’m afraid you have a bearing issue, but as you need to set the valve clearings anyway, it is a good starting point.

one additional thing: have you checked the exhaust pipes and silencer for not being loose ? Another possible culprint.
luck with the project