Yanmar, White exhaust smoke

[Verl790]

Dehler 29 with Yanmar 2gm20f. Engine starts and runs normally for a time then the revs increase momentarily combined with large amounts of white smoke billowing out of exhaust, the engine then stalls. There is also an oil film left on the water (unburnt fuel?). The engine will restart and run normally for a while until the process starts again. If I close the throttle quick enough the engine will continue to run. Fuel filters are clear and there's water coming from the exhaust when engine is running. What can be the problem? Your thoughts will be gratefully received

Verl

 

[Cheesey69]

Sounds like leaking injector. White smoke usually means un burnt fuel.

 

[Malish]

Need some times - how long is 'for a time' ?and how long before you try to restart the engine?

 

[Topcat47]

Black smoke is usually unburnt fuel.

 

[Sneaky Pete]

Last time I saw something like that it was the pump timing that had slipped. As said it appears to be unburnt fuel

 

[ex-Gladys]

Black smoke is usually unburnt fuel.

...errr, no... Black is over-fuelling, black is carbon = too little air for the fuel delivered (i.e. engine revs too low for governor demand)

 

[Biggles Wader]

...errr, no... Black is over-fuelling, black is carbon = too little air for the fuel delivered (i.e. engine revs too low for governor demand)

I think that is what is meant by "unburnt fuel".Too much fuel for the amount of air means incomplete combustion and black smoke results.Either way we will learn more when the OP comes back with further details.

 

[RichardS]

I think that is what is meant by "unburnt fuel".Too much fuel for the amount of air means incomplete combustion and black smoke results.Either way we will learn more when the OP comes back with further details.

Not quite. Over-fuelling means that the fuel is being burned but there is more of it than the engine actually needs and black smoke is produced from the fuel that is burned surplus to requirements, so to speak.

White smoke usually results from unburnt fuel due to the cylinder conditions not be right for proper combustion. There might be too much or too little fuel but it not being burned is the issue.

Richard

 

[vyv_cox]

Black smoke is due to incomplete combustion. There is insufficient oxygen for the amount of fuel, so instead of complete combustion to carbon dioxide and water some of it only gets as far as carbon and water, hence the black smoke. Historically, trucks struggling up steep hills, 'belching black smoke'. Foot hard to the floor, maximum fuel injected but no corresponding speed.

White smoke is fuel, with no combustion at all. In winter our old engine is reluctant to start if I get the pre-heat wrong, with the result that copious quantities of white smoke are emitted before it finally fires up.

 

[Verl790]

Need some times - how long is 'for a time' ?and how long before you try to restart the engine?

Depends on how much throttle is opened. At low revs the engine will run for over an hour before it loses power, produces the white smoke and stalls. Engine will start after a few minutes rest and will run normally - until the next time.

 

[Cheesey69]

As a plant fitter I would start with the easy stuff and that would be to check with your injectors are leaking or not shutting off properly or the spray pattern is weird then I would go to the high pressure injection pump for timing issues or other fault but I would really start at the injectors and then look for other things first but I've had this before when the combustion Chambers slowly filled with diesel because the injectors are not shutting off properly the engine run off a little bit and then shut down because of too much fuel

 

[Verl790]

Good advice. In the light of what you say, getting an engineer to take a look may be the best option
Thanks to all

 

[stevd]

Could be either air getting in the fuel system, or your injectors need a service.

 

[Flica]

having bitter experience of raw water-cooled 2GM, producing occasional white "smoke" (actually steam).
Cylinder head leak from water passage just behind #2 cylinder. Easily corrected by head off, light mill and replace with new gasket.
Don't leave it - it will corrode the walls of #2 cylinder.
First happened to me in the Raz du Sein!!
Ended in le Conquet 30 hrs later after the head gasket blew out altogether.