Smoking Yanmar engine

[BartW]

We did valve clearance and injector test (all ok) on our 4cyl Yanmar / kohler engines / generator. They have approx 4000hrs on them, the injectors are only 350hrs,
one generator still has a bit too much smoke ( dark blue grey).
What could be the cause?
New oil level is slightly above max?
Does it make sense to have the injection pump refurb ?
Anything else?

 

[Portofino]

It’s burning off the excess oil .
Excess crank case pressure from over filing generates fumes which in tern are fed back into the air intake system to be burnt off by a breather .

 

[Momac]

Extract oil until not above the max.

 

[Assassin]

Bart, until you rule out many potential issues why spend the money only to find it wasn't the problem, getting the correct oil level is a first.

Identify the smoke and its colour as this will identify the problem, dry black smoke is usually overfuelling and this generally rules out injection pumps as they are overfuelling and not underfuelling, so look at the air intake side and check your air filter, run it without the air filter fitted for a couple of minutes and no more, and see if the smoke disappears. Porto is correct in that piston blow by is almost a certainty of you have overfilled it with oil and a proportion of the combustion gasses will blow past the piston rings and into the sump, and on induction strokes these same gases will return the opposite way past the piston rings and be burned off during combustion, and over time your piston rings seize partially or fully as they either gum up or fill with carbon deposits.
Try a decent brand of slow acting diesel injection system cleaner and put this into the fuel as this will clean the varnishes and carbon deposits and allow the piston rings to move correctly in their grooves, and if it contains a piston ring lubricant then so much the better.

 

[Portofino]

Bart, until you rule out many potential issues why spend the money only to find it wasn't the problem, getting the correct oil level is a first.

Identify the smoke and its colour as this will identify the problem, dry black smoke is usually overfuelling and this generally rules out injection pumps as they are overfuelling and not underfuelling, so look at the air intake side and check your air filter, run it without the air filter fitted for a couple of minutes and no more, and see if the smoke disappears. Porto is correct in that piston blow by is almost a certainty of you have overfilled it with oil and a proportion of the combustion gasses will blow past the piston rings and into the sump, and on induction strokes these same gases will return the opposite way past the piston rings and be burned off during combustion, and over time your piston rings seize partially or fully as they either gum up or fill with carbon deposits.
Try a decent brand of slow acting diesel injection system cleaner and put this into the fuel as this will clean the varnishes and carbon deposits and allow the piston rings to move correctly in their grooves, and if it contains a piston ring lubricant then so much the better.

That’s not what I said and apologies for not seemingly making myself clear.

It may be correct what you said , leaky rings but @ 4K hrs those engines , Yanmar will have I reckon tight pistons .
They will get up to temp and expand and fit in the normal way .....accepting a little blue smoke for few mins post start up .
Other wear inducing routes of oil , excess oil into the combustion C is the valve guides ....again assuming they are within spec .

No ....my suggested route is the lower part of the engine s crank pressure under the pistons due to overfilling .
The oil mist / foam created by the crank splash is escaping naturally via the crank breather recirculating system ( a primitive emissions system ) wherby the crank fumes are basically fed back into the induction side ....There may be a filtration system of sorts or not !
A little fumes is normal ,excessive ......then blue smoke .

Any blow by that you suggest ( compression escaping down from the cylinder via the rings ) can be usually be diagnosed by removing the oil filler cap on the rocker box if it has one , or crank side i guess and putting your hand , the palm over to feel the pressure or watch fumes come out .

Bart remove the oil filler caps of both engines running and compare “ palm pressure “

For my Dx , there may be a v slight difference in “ palm pressure “ but hardly noticeable.If you remove the air filter or open up the air box ( sorry I,am not familiar with this exact set up ) .......if the crank case pressure is higher than spec then there will be an oil mess in the air box , or the induction apparatus past the air filter .

Additionally if it were loose rings from poor fit the oil level will continue to drop as it would constantly be burning oil ...blue smoking all the time .

Speaking generally while on topic some air filters are throw away paper cartridges others are reusable .Theses are a plastic mesh you clean in spirt solution the re oil up .A fine film of oil is added back to the mesh to collect the dust .Its possible if they are over oiled ...that’s another ( albeit temporary) source of excess oil into the C chamber and blue smoke as it’s burnt off .
Walker do an “ air step ‘ marine reusable air filter and you supposed to use there special oil .
Personally I prefer throw away paper cartridges......cars + boats any IC .

But as said establish spec oil level first .

 

[B58]

We did valve clearance and injector test (all ok) on our 4cyl Yanmar / kohler engines / generator. They have approx 4000hrs on them, the injectors are only 350hrs,
one generator still has a bit too much smoke ( dark blue grey).
What could be the cause?
New oil level is slightly above max?
Does it make sense to have the injection pump refurb ?
Anything else?

Blue grey smoke indicates that there is water in your fuel, the grey part is the water steam and the blue indicates incomplete combustion due to the amount of water in the fuel, check you pre-filter for water, and fuel tank?

what fuel are you using?

 

[BartW]

thank you all for advice,
some simple things to test first
fuel is same for engines and other genny, those have much less smoke,

 

[BartW]

oil level is now 3/4 between min and max
pre filter replaced, main filter was replaced earlyer this week
Cranc breather hose disconnected,
now running for 30min, (reached normal operating temp)
power output approx 4amps@230V

but still the same smoke,
dark grey blue ish

see pics below






welcome any advice !

 

[vas]

welcome any advice !

use the starboard one when stationary and this one underway!
you're lucky to have two

my small 2cyl 2GMF also smokes following a full rebuilt, but I put it down to the underwater exhaust conversion that eventually leaves only most of the gasses to exit through the fart pipe (it's complicated and haven't investigated fully tbh) and the fact that it never heats up properly, have to check the thermostat (not even sure it's there and not thrown away by PO)

cheers

V.

 

[Portofino]

Just before we go any further this all started after you did the “valve clearance and injector test “ ........post #1 ?

No smoke before ?

 

[BartW]

Just before we go any further this all started after you did the “valve clearance and injector test “ ........post #1 ?

No smoke before ?

same smoke as before valve clearance / injector test.

 

[Portofino]

Stop worrying.
Yanmar s in the Far East have hard lives and go on for ever .

Carefully monitor the oil level over the next 100 hrs , if necessary top it up .

 

[BartW]

use the starboard one when stationary and this one underway!
you're lucky to have two

my small 2cyl 2GMF also smokes following a full rebuilt, but I put it down to the underwater exhaust conversion that eventually leaves only most of the gasses to exit through the fart pipe (it's complicated and haven't investigated fully tbh) and the fact that it never heats up properly, have to check the thermostat (not even sure it's there and not thrown away by PO)

cheers

V.

we are already used to this routine , more or less, because we hardly ever run the genny during navigation,
but for the automatic start (battery SOC 60%) around 6am, we use the smoky genny.

also another routine, when cold, each genny needs 2 starts attempts, the first it switches off because oil pressure comes up just a bit too slow,
(the safety system switches the engine off after the frist start attempt)
I might change a capacitor, and make that period just a fraction longer (or that capacitor might be very old / dried out / wrong value)

 

[BartW]

actually on both genny's clearance on some valves was far out of spec,
on one we found a gap of at least 5mm ! (spec is 0.2mm) the metal cap on the rod was off !
on the smokey one also a few valves with 1 or 2mm clearance,
I think that the valve clearance of these units has never been adjusted
apart from the smoke, these are really bullit proove workhorses...

 

[Portofino]

we are already used to this routine , more or less, because we hardly ever run the genny during navigation,
but for the automatic start (battery SOC 60%) around 6am, we use the smoky genny.

also another routine, when cold, each genny needs 2 starts attempts, the first it switches off because oil pressure comes up just a bit too slow,
(the safety system switches the engine off after the frist start attempt)
I might change a capacitor, and make that period just a fraction longer (or that capacitor might be very old / dried out / wrong value)

What oil W are you putting in ?
when did you last change the filter?

A thinner oil will pressure up faster .
thinking 0W 40 , or what I use in Ferrari is 10W 60 ....same a BMW “ M “ sport I mean proper M s .
Needs to be thin 10w when cold to spread out first ....then capable of withstanding heat hence the 60 .
Theres is downside , it’s expensive and as thin as dishwater so it find leaks that were not there before because it’s so thin and runny but gets up the pressure the most rapidly.

 

[BartW]

What oil W are you putting in ?
when did you last change the filter?

A thinner oil will pressure up faster .
thinking 0W 40 , or what I use in Ferrari is 10W 60 ....same a BMW “ M “ sport I mean proper M s .
Needs to be thin 10w when cold to spread out first ....then capable of withstanding heat hence the 60 .
Theres is downside , it’s expensive and as thin as dishwater so it find leaks that were not there before because it’s so thin and runny but gets up the pressure the most rapidly.

filters and oil are all new
oil type 15W40 same like engines,
don't intend to buy special expensive oil just for that ...(and not even be sure that it will solve the start problem)

 

[Portofino]

actually on both genny's clearance on some valves was far out of spec,
on one we found a gap of at least 5mm ! (spec is 0.2mm) the metal cap on the rod was off !
on the smokey one also a few valves with 1 or 2mm clearance,
I think that the valve clearance of these units has never been adjusted
apart from the smoke, these are really bullit proove workhorses...

Valve guides could be worm .A big gap means a shorter episode of movement, opening late and closing early . I think that leads to excessive cylinder temps ....conducted through the valve to the stem over dimension to friction on the guides .
They bore them out = oil seeps back down ...esp when cold .

what should they be ....inlet 0.5 , exhaust 0.6 mm ? .......crikey 2 mm that’s huge .

 

[B58]

Valve guides could be worm .A big gap means a shorter episode of movement, opening late and closing early . I think that leads to excessive cylinder temps ....conducted through the valve to the stem over dimension to friction on the guides .
They bore them out = oil seeps back down ...esp when cold .

what should they be ....inlet 0.5 , exhaust 0.6 mm ? .......crikey 2 mm that’s huge .

0.2mm or 8thou in old school

 

[B58]

thank you all for advice,
some simple things to test first
fuel is same for engines and other genny, those have much less smoke,

Looking at the pictures it looks like unburnt fuel how many hours on the engines are they running at 3000rpm or 1500rpm do the genny's run for long periods on low load setting you say 4amps at 230v = 1Kw do they just charge battery's?

 

[BruceK]

Blue smoke indicates oil being burnt. This can happen in the following ways:

• Worn valve guides or seals - This would be my first port of call given the gaps and neglect you were reporting.
• Wear in power assemblies (i.e. cylinders, piston rings, ring grooves) - at 4k hours this by consensus seems unlikely.
• Cylinder glaze - If the engine spends most of it's life ticking over and not coming up to temp this is a potential
• Fuel dilution in the oil (oil thinned out with diesel) - not sure with your engine but I have heard some lift pump seals can wear allowing diesel to leak into the engine. Sticky rings, glazing (bore cross hatching wear) etc. Monitor oil pressure and levels.