White smoking diesel

fredcb

fredcb

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Our previously reliable YM20 has suddenly lost power and is gushing white smoke. This has occurred immediately after filling the tanks up with diesel. Can this be a coincidence? Thoughts that are occurring to me are piston rings, head gasket etc, but the engine is running smoothly without vibration which suggests both cylinders are firing.

Has anyone any advise?
 
There are two kinds of white smoke: one is steam from the exhaust caused by reduced water flow allowing coolant to boil in the exhaust. The engine itself may not be overheating. Have a look at the exhaust elbow and check it is not chokedand restricting the water supply to the exhaust.

The other is diesel 'fog' - unburnt diesel spray. This is lingering and much more pungent than exhaust steam. Causes can be partial fuel blockage, injector fault, low compression. Usually compression problems are accompanied by poor starting, particularly from cold. If you had just fuelled up, I would suggest you check your fuel filters and fuel system to start with. Mechanical problems are usually accompanied by mechanical noises - clicks, knocks, rattles etc.
 
sounds like fuel problem. possibly quality of the fuel you bought, or maybe it stirred up something lying in your tank which has found its way into the fuel system. Filters and sediment bowl should have a story to tell you.
 
I'm more familiar with petrol engines. Perhaps you'll forgive a question based on my ignorance of diesel engines.

Why does a fuel blockage result in a fog of unburnt fuel? I'd have expected a blockage to reduce the amount of fuel getting through so that everything that did get through would be used (but not very efficiently because of the lean mixture.)

Looking at the problem from the other end, the diesel fog is produced by the injectors so fuel is getting to the cylinders. That fog is then being expelled from the cylinders and is not being fully burned. Wouldn't that happen if there wasn't enough compression to ignite the fuel (piston rings? loose injector? damaged exhaust valve?) or if the compression were being released too early (timing problem?)
 
I must admit that low compression was my first reaction, but I just cant get over the coincidence of having just filled up the tanks which I would guess is likely to have stirred up all kinds of crap.

Of course there is a lesson to be learnt here about not leaving diesel tanks low over the winter, but that is difficult when one uses the boat all through the year.
 
Have you got a water seperator in the fuel line? Check the glass under the filter (if you have one). Last season, I took on board some contaminated deisel, the water therein took a few days to settle in the tank and then the engine stopped.....could have been nasty.

The bottom two gallons in the tank was around 75% water....
 
Don't discount the possibility that you have a restriction in the water injection section of the exhaust. The restriction would account for a loss of powver, and the white smoke - the overheating exhaust.

Good luck!
 
My belief is that a blocked fuel causes restriction. Similar basis to a restrictor fitted to motorcycles to reduce their power. It is that the pressure in the line is not able to be maintained, thus resulting in poor atomisation throught the injectors. Try depressing an aerosol can part of the way down and you will notice that it does not atomise properly. Max atomisation = max power! Poor atomisation results in unburned fuel.

Hope that helps.
 
I have removed the filter and water trap and the filter was so clogged with gunge it is possible that this was restricting the fuel flow to the engine. I have fitted a new filter and this seems to have cured the smoking though I shall not know for sure until the next run in earnest.

Thanks everyone for your advice
 
Near, but not quite right Abestea! Diesel works by compression ignition. If insufficient fuel is injected then it simply does not ignite. It can also start to burn, but the flame becomes extinguished before all the fuel is burnt, so that a spray of unburnt fuel passes through to the exhaust. Also if the injector spray pattern is faulty, the same thing happens, only the good part of the spray ignites, the rest just gets passed through. This happens because diesel is much less volatile than petrol. But like petrol, insufficient air/fuel mix will cause ignition failure and white smoke even though the engine may still run at reduced power/speed.

Diesel research engineers spend much of their time working to ensure the flame actually consumes all the available fuel in the combustion chamber efficiently.

Seabee, I would be reasonably certain you will have solved your problem. You need to try and find out if there is still muck in your fuel tank. If you had a load of dirty fuel, you will go on getting problems until it has all been cleaned out. Not fun!
 
My white smoking (Volvo 2003 28hp) at start of last year's season was bug contaminated fuel. Had it all pumped out, through filter and then back in with shock dose of 'Fuel Set'. Cured.
 
Generally........blue smoke = oil being burnt. Black smoke = fuel problem. White smoke = water ingress into engine.

So, 'gushing' white smoke, AND loss of power could mean head gasket leak. Have you checked compression in each cylinder? Is there any sludge in the oil? If you have the engine 'marinised', is there any frothiness in the cooling system? Do you always fill up with fuel at the same place....is the fuel reliable and water free? Do you leave the boat with empty fuel tanks over winter and allow condensation to form?
 
Good reminder re filters, need to change the engine mounted ones which might solve my unburned fuel smoke issue. Injectors were all done and injector pump timing has been fiddled with. Unless Mr LSUK gave me the wrong injectors back. I 'fess they looked the same so I didn't check the part#.
 
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