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Thread: Mitsubishi L3E problems

  1. #1

    Mitsubishi L3E problems

    Hi all,

    I'm trying to diagnose a problem with my Mistsi L3E fitted to a Volvo mini excavator (271 I think)..

    Anyway after some hard starting and I think loss of power (stalls whilst digging etc.) , I've pulled the engine out to investigate.

    I've looked through a few really good threads on this site about this engine, and I think there are a good few experts around here that know thier stuff, so thought I'd try a couple of questions..

    1)

    On checking the compression (whilst running the starter) I get around 210psi. This was pretty similar on all cylinders..
    From the L3E Manual it shows the pressure should be 413-455psi, so according to this I'm way off.

    Does this pressure reading from the manual sound right ? It sounds quite high to me (the compression ratio of the enigne should be 23-1, so maybe should be more like 338psi (14.7 * 23 = 338) ?

    I'm not sure I'm checking the pressure reading I'm getting against the correct value..

    2)

    It seems the pressure is down whichever value I check against,so I'm trying to find out why.

    The cylinder widths look pretty correct at 76mm, or thereabouts (within limits).

    I can't see any cracks etc.

    The rings were the next obvious thing, 1 measured gaps of:
    No 1 - 0.7mm
    No 2 - 0.55mm
    Oil - 0.55mm

    I'm not sure if this is a problem ; the manual gives the 'Standard' gap as 0.15 to 0.30mm, and a service limit of 1.5mm

    It only recommends replacing the rings if they are above the service limit.

    What is the difference between the Max 'Standard' gap and the Service Limit ?

    Mine at 0.7mm are above the Max Standard Gap, but below the Service limit. Would you think they need replacing ?

    Probably more to the point is do you think that even though they are below the service limit, they could be accounting for the loss of pressure (@200psi according to the 413psi figure in the manual) ?

    Would this 'extra' gap or wear account for this much pressure loss ?

    I did clean up 1 set of valves and seats and re-tested, I got about another 20-30psi, so I reckon with a good valve cleanup each cylinder would probably give around 230psi.. Still pretty low, would the ring gap account for this ?

    Thanks for any help!

  2. #2
    Fabrication Guru +1 v8druid's Avatar
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    how dry were the bores when conducting your tests? ... i.e. ... had it been stood a long while ?
    If it's got tracks, wheels, t*ts, or an engine, at some point it's gonna give you trouble!!

  3. #3
    Quote Originally Posted by v8druid View Post
    how dry were the bores when conducting your tests? ... i.e. ... had it been stood a long while ?
    No, it had been running recently, couple of days before maybe..

    I'd been replacing the injector jets and testing them, but since that id had real trouble getting it running again.

    I gathered the next step was to check compression, and came up with the results above..

  4. #4
    Nothin' but trouble Muz's Avatar
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    Hi & welcome .. I had this issue about the pressures not being the same in the manual also, I cant remember about what the discrepancy was, but it turned out to be a red herring .. that engine will run and run, with a wide variance of wear, its usually the control gear around it that fails first. That said... if its been tipped on its side and not shut off fast enough, it will heat a main bearing shell and start to pick up real quick which will run the bearing .. then you'll get low compression, but you would hear that, and also see some smoke and lose a lot of power. In this state the engine will die quite quickly, so if its not there yet, theres no smoke, and you cant hear any rumbling, chances are it will be ok .. how many hours are on it ? how old is it ?pics ?
    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
    Nothin' but trouble Muz's Avatar
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    You and mowgli might be in the same boat see here http://www.plantandconstruction.co.u...t=L3E+guvernor
    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

  6. #6
    Quote Originally Posted by Muz View Post
    Hi & welcome .. I had this issue about the pressures not being the same in the manual also, I cant remember about what the discrepancy was, but it turned out to be a red herring .. that engine will run and run, with a wide variance of wear, its usually the control gear around it that fails first. That said... if its been tipped on its side and not shut off fast enough, it will heat a main bearing shell and start to pick up real quick which will run the bearing .. then you'll get low compression, but you would hear that, and also see some smoke and lose a lot of power. In this state the engine will die quite quickly, so if its not there yet, theres no smoke, and you cant hear any rumbling, chances are it will be ok .. how many hours are on it ? how old is it ?pics ?
    I'll try and dig out the info tomorrow evening, it has about 3000 hours on the dial, but who knows if it is authentic..

    I brought it a couple of months back, and lets just say it wasn't 'correctly' advertised, so I suspect about 2001 model digger.

    To be honest once its started up it dug reasonably well, no smoke of any kind, until I hit the stalling issue.

    When started from cold I could run any service all the way to the stops, and it would labour slightly but continue running. I thought this meant the MRV valve was working ok, and everything was fine.
    After about 10 mins, I suspect when the oil warms up, holding the same service to the stop caused the engine to stall. It was then pretty difficult to get going again - sometimes it would , sometimes not.

    Sometimes when it did start, it sounded like it was running on 2 cylinders, for about 15 seconds, then the third would kick in.

    I started reading through a really good thread on here about an EC15B - and got a tester to test the hydraulic pressures when it would stall the engine.
    I found it would put out about 160psi before stalling, which I don't think is all that bad.


    So i starting chaning a few parts to try and find any problem its got:

    All Serviced - Filters etc replaced - Found air filter completley missing , one fuel filter torn through ...

    New Glow Plugs

    New injectors (jets replaced) - tested and spraying ok at just under 2000psi (I think one or two of these were a bit dodgy before,leaking etc.)

    IP pump taken to pieces and cleaned - Found one 'supply' of the pump had ceased - the 'piston' wasnt being pushed back down by the spring..I wondered if this was causing the 2 cylinder startup, until the engine vibrated enough to make the piston move again..

    This is all back together and i've tested it spraying fuel from all injectors, looked ok to me. Only problem with this is that I think I have moved the nuts that hold the top of the IP pump cylinders in place, and hence screwed up the volume of fuel they deliver. In the manual it does state not to move these unless you have a pump testing tool - well I'm a bit late for that

    Once I'd got all that back in place it just wouldnt start not matter what - some white smoke now comming from exhaust - my guess is now either too much fuel comming from IP pump, or compression problem - I can't think of anything else.

    I don't have any expereince with these engines - is the fuel 'volume' that critical ?

    So whilst looking at the cylinder pressures and seeing them almost half what the manual says, I though I might as well get the head off and see whats under there.
    And it doesnt look that bad at all - which is leaving me a bit stumped as to the pressure loss problem.. I just wondered if anyone had changed the piston rings and if they had noted the pressure difference they would give..

    Overall, I think you might be right about the controls/fuel - I clearly need to setup the fuel system properly again.. But whilst I had it in bits I thought I might as well check eveything else , and try and sort out this pressure problem..



    Thanks,
    Rich.

  7. #7
    Quote Originally Posted by Muz View Post
    You and mowgli might be in the same boat see here http://www.plantandconstruction.co.u...t=L3E+guvernor
    Yeah sounds interesting, I'll have a look at that whilst its in bits..

  8. #8
    Nothin' but trouble Muz's Avatar
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    Sounds like youve worked through the important things ok What you need to be aware of is the pump sits on shims. These shims determine the pump volume/timing if I remeber correctly. Its quite a good system in that you never need to time the pump as such, because the cam below that drives the pump members, is still connected to the crank in the timing case. ... but adjusting its height will affect the engine performance. Ive never had to alter any, so theres no info on the forum about it, but have a hunt and see if you can come up with something along these lines. If someone has had the pump out, they may have discarded a shim by mistake, or , fitted a gasket, thinking they were doing the right thing to seal up the injection system, without realising they've just altered the height of the pump off the cam lobes, thereby affecting its performance.
    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

  9. #9
    So I've done a fair bit of work on this thing, and got nowhere!

    Had the initial problem with low compression, so hauled out the engine and changed all piston rings - they didn't look all that bad,but once finished and after cleaning and grinding the valves the pressure was back to around 400-410 psi..

    Got it all back in the digger and it wouldnt start. The starter was pretty knackered so its now been swapped for a new one, and turns over nice and quick (probably double the old).

    Still nothing, so injector nozzles have all been replaced (with new). Setup to correct PSI, but seem to be a little 'temperamental' i.e. sometimes they test fine, then ill try again an it dribbles, then its fine again. Is it possible that the springs in the injectors are just a bit old ? Do they wear out ?

    Also I've had to dismantle the IP pump, as one of the plungers was sticking. Ive had this thing in and out of the engine too many times to remember !

    I've tested it in the digger with the injectors connected but outside the block , so I can see them spraying.

    Last time I checked they were all spraying ; I have no idea if its the correct quantity of fuel ; also with the slightly dodgy injectors , every now and then 1 will stop spraying then start up again.

    Once I confirmed there was fuel getting out, I put them back in and tried again. It sounded as if one clyinder or two were about to go , but just wouldnt start properly.

    Has anyone seen this type of problem before in this engine ? As far as I can tell it should run - theres fuel, the glow plugs works (new as well and confirmed working) ,it turns over quickly, just won't bl**dy run :)

    I am suspecting the IP pump is either too worn or knackered in some way, and won't put out the correct pressure, or maybe not reliably enough. Its confusing because when testing the injectors I can see them spraying ; so hope they should be fine.

    Also coupled with the maybe slightly worn injectors its a nightmare to diagnose.

    The only thing I can think of now is to replace the IP pump and 3 Injectors with new... But this will be big money I think !

    But before I do that can anyone this of something I may be setting up incorrectly ? I'm wondering if too much fuel ???

  10. #10
    Nothin' but trouble Muz's Avatar
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    Did you have the crank out and removed from the timing assembly ?
    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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