hey guys I had my engine rebuilt on my mm 30 misubishi this spring, from new crank up,pistons,rings,bearing, head redone,ect, after 50 hrs, after the rebuilt the engine still has a steady stream of blue smoke,so bad it over come you burns your eyes,i think new rings should be broken in by now,what to look for,to do a compression test do you pull out injectors? I rebuilt several gas engine in my life, did not want to try the diesel,guess I should have
Does it have a turbo? If so you could have oil passing there. If you have glow plugs you can compression check by removing them. 350-400 psi is good. As for the rings some oil rings and compression rings are specifically oriented. And the gaps should be clocked.
no turbo,3 cyc,about 23hp,i want to check some thinks out before I call the guy who did the job!
Problem on all diesels is that you have to load the engine hard to get the rings to seat. Excavators don't generally put that hard of load on all at once. You have to run multiple functions or defeat the load limiting systems on the machine for a bit to get the firing pressures up high enough.
Good day If you leave a new engine to idle for long periods that can cause the bores to glaze, making a compression check should show up a ring issue, only other part that has not been mentioned is that of valve guide seals. Kind regards uffex
Is it using oil and or have excessive blowby? Could the fuel system be out of time a bit?
This one good example why diesel engines used in this setting should be run and broke in on a dyno. JMHO
the rebuild included the head being redone also,it not using oil,i put about 50 hrs on it since rebuild,i don't see anything on the injector pump for timing,this is a maching from the 90s, simple, K3G mitsubuishi engine,these machines were built with CAT,302 size undercarriage takes cat parts,cat used a lot of Mitsubishi engines,thanks for the help!!
Blue smoke is indicative of oil consumption, monitor the level closely. What grade of oil did you use for the initial break in? Was it synthetic? Generally, if the exhaust is burning you eyes, its usually raw fuel from incomplete combustion, this could be from poor injection timing, or the cam being off a tooth in the gear train. Is the motor running rough? Was the injection pump overhauled as well?
A lot of piston rings that come from Asia are not beveled, they are perfectly parallel to the bore. So instead of the bottom edge of the compression ring touching the bore, the entire edge contacts the bore. This greatly hinders seating.
the injection pump was sent out and checked? the injectors were tested,dont no what oil he put in for break in I just changed it at 50 hrs with 15-40 rotella,the engine runs smooth,starts great,just smokes like crazy,new glow plugs also,the engine would bog down and stall before the rebuild, 1 piston ring was broke,bad rod bearing,the rebuilder said he honed the cyl,funny there was no ridge at the top of cyl-none,
Some engines it's critical that the angle of crosshatch be right on the money when a cylinder is finish honed. For instance the Cat 1160 and 3208 had a specific angle.
What I’ve see with Japanese engines is they use hardened liners and you don’t see ridges worn at the tops unless you have a broken ring or something wrong with an injector. Honing then to use again is pretty tough. I’ve used coarser stones to actually break the glase. When you go to that amount of repair you need to do extra things like checking liner taper and ring end gaps for a successful rebuild.
Hard liners and tough ring material you won't necessarily see much ridge. When moly rings came on the scene cylinder ridge became a small factor.
I might expect a ridge on an engine with lots of hours, but if I'm tearing it down for one broken ring I might expect a groove parallel to the stroke instead.