Yanmar white smoke

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Yanmar white smoke

Postby mike cunningham » Wed Apr 19, 2017 4:19 pm

My trusty 2GM20F has been running flawlessly for many years. Sooner or later I was bound to run into something I was going to have to deal with.

For the last 50 or so hours of operation I have noted an excessive amount of WHITE smoke along with a very obvious fueley smell.

Given the boat completed a sail to Hawaii and back last year, a trip which included a lot of at sea refueling from 5 gal jugs, I figured first step would be to completely clean tank, filters and lines up to the hi pressure fuel pump. Accomplished this and also upgraded the primary filter to a compact Racor fuel water separating filter assembly with a bowl. Previous filter was just a filter, no observation bowl. Also purchased a diesel dry additive to enhance water protection and to clean injectors to the extent an additive can actually clean them. I did find some debris in the tank and some slight gelling plus quite a bit of dirt and a little water. It was not a shocking amount of contaminate. I have now run about 20 gals of known clean and treated diesel through the system and white smoke is still an issue.

Oil burn seems minimal minimal - about 8 ounces per 40 hrs running (engine hours at about 1800 - best estimate including WAG on POs usage)
No coolant is being consumed
Engine power is nominal at all RPM
engine runs well, no weird noises
Air cleaner has been replaced and is clean
I did note hard starting in colder weather (40s 50s) but this symptom seems to have cleared with warmer weather (60s) and possibly clean/treated fuel benefit. Engine historically started up quickly in all weather here in California.

The plan going forward is:

1. perform compression test - tools on the way - if this fails I need to reboot my strategy, I am banking on compression being OK due to overall engine performance being OK
2. Remove and replace both injectors - injectors on the way (never been replaced during my ownership - 1200 hours)
3. perform valve clearance inspection and adjustment - never been done (yea, I know)

Anyone have any other thoughts?
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Re: Yanmar white smoke

Postby GeoffSchultz » Wed Apr 19, 2017 6:33 pm

[Stolen from another web site]

White smoke is caused by raw, un-burnt fuel passing into the exhaust stream. Common causes include:
· Incorrect fuel injection timing
· Defective fuel injectors
· Low cylinder compression

Low cylinder compression may be caused by leaking valves, sticking piston rings, ring wear, cylinder wear, or cylinder glaze. When white smoke occurs at cold start and then disappears as the engine warms up, the most common causes are fouling deposits around piston rings and/or cylinder glazing.

Continuous evidence of white smoke indicates a mechanical defect, or incorrect fuel timing.
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Re: Yanmar white smoke

Postby Hans » Thu Apr 20, 2017 2:46 am

The causes Geoff mentions give a white/ light grey smoke which also stinks.
Another cause and giving white smoke which doesn't stink: too little water injection in the exhaust system
resulting in a too high exhaust temperature giving water vapour.
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Re: Yanmar white smoke

Postby mike cunningham » Thu Apr 20, 2017 12:47 pm

Thanks for the responses guys.

It looks like my plan is consistent with the possible faults.

I believe I am good on water flow through the mixing elbow/exhaust. I replaced the elbow several years ago due to zero water flow so been there done that. Today I have excellent flow through the system as evidenced by good water flow at the exhaust, no overheating indications including smells of burning rubber and the like.

I am really hoping it is the injectors which seem the most likely suspect. Compression issues sound like money unless it is something simple like poorly adjusted valve clearances. Fuel injection timing might also be fixable on a DYI basis but the procedures to time the fuel injection look tricky.

As a general note, it is too bad there is not a comprehensive fault tree on these engines. I have to believe that there are other indicators of, say injector issues vs compression issues but nothing I have seen takes you to the next level. You read white smoke could be caused by these six things. Fuel smelling white smoke with no oil burn and no coolant burn reduces the possibilities but then the fault tree seems to come full stop. Seems like there could be some further indications which would lead you to suspect injectors vs compression but I've not been able to find these discussed anywhere.
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Re: Yanmar white smoke

Postby mike cunningham » Tue Apr 25, 2017 2:41 pm

Got my compression tester and rebuilt injectors plus all needed tools, so now we will find out what is what. I will keep you all posted.
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Re: Yanmar white smoke

Postby mike cunningham » Thu May 04, 2017 5:20 pm

Completed a valve adjustment, no help

replaced the injectors with rebuilt units and she fires up and runs just like she used to. No white smoke, all is good.

Bottom line was an injector issue. I bought three rebuilt injectors, replaced both in the engine so I have one left. I will hove one of the two originals rebuilt in order to have a complete set of spares on the boat. Learned a lot doing this project myself, very worthwhile.

I never did a compression test. I was saving that for last ditch effort if injectors did not work.
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Re: Yanmar white smoke

Postby GeoffSchultz » Fri May 05, 2017 5:23 pm

Glad t hear that it was a relatively simple fix and you learned a lot while doing it.

-- Geoff
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Re: Yanmar white smoke

Postby mike cunningham » Fri May 05, 2017 8:16 pm

I bought a torque wrench for this project (about $35 on Amazon) this was really useful. When I pulled the injectors I felt like the hold down flanges were not very tight. Now I am sure they are torqued to factory spec.
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