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White smoke / BMC


Traveller

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Now I know this subject has been done to death but this is a bit different. I get white smoke at start but it ceases very quickly and the engine runs clean. Starting is brilliant in the warmer months, although it can struggle a bit in the colder months. It is only on extremely cold days that it can be a bit of a pig but again it starts and the white smoke clears quickly. What I have noticed though is that if I rev the engine up very quickly/aggressively (even when hot) there is a degree of white smoke. It goes once the engine catches up with itself (if you get my drift). The white smoke does not arise if I open the throttle more slowly. Thoughts please?

Colin

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White smoke is either water or unburnt diesel.

 

Stick ya hand in the smoke and then sniff ya hand, if it smells like diesel it’s unburnt diesel. 

 

My my guess from your description is that it’s unburnt diesel, but other more experienced bods will come along to confirm on why.

Edited by Robbo
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Our BMC starts with white smoke for a few seconds which then clears as the engine warms up. We get some black smoke when we have to rev hard for some reason. I'm not worried by this as 99% of the time the engine does not smoke. It is starting to show its age having now done 10750 hours or thereabouts but while it still goes I won't be fixing it!!

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19 minutes ago, Robbo said:

White smoke is either water or unburnt diesel.

 

Stick ya hand in the smoke and then sniff ya hand, if it smells like diesel it’s unburnt diesel. 

 

My my guess from your description is that it’s unburnt diesel, but other more experienced bods will come along to confirm on why.

Or late Injection Timing ,speshly if it is a 1.8 BMC as the Timing Chain will stretch with age. 

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42 minutes ago, Traveller said:

What I have noticed though is that if I rev the engine up very quickly/aggressively (even when hot) there is a degree of white smoke. It goes once the engine catches up with itself

It’s slightly over-fuelling until, as you say, the engine catches up with the fuel delivery. 

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Not something I was particularly planning on bringing up on here, but whilst we're on the subject: my BMC 1.8 smoked significantly when running it at higher throttle settings until I cleared out the inlet water filters to improve the cooling flow. When I initially noticed this the temperature gauge showed a significant increase - at which point I stopped and cleared out the mudbox which fixed it. However subsequently I got the same issue without an elevated temperature being indicated - cleaning out the water filter did fix that though (and I don't now seem to have any issues on canals - running full throttle on the river does still seem to result in some smoke, though I only have to back off a little to get rid of that without a huge decrease in speed).

 

I'm guessing this is standard stuff - it didn't require any particular genius to work out what was happening and the likely solution.

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The poorer cold starting at low temperatures suggests there may be a glow plug problem or in the case of the 1.5 and a very few 1.8s with pin type plugs the plugs need removing and their "pin hole" cleared of carbon. So in the case of the OP, which engine. If its a 1.5 that ha snot had its glow plugs out for a long while you will need to worry them out by tightening a small amount the loosening a similar amount many, many times until you eventually get the n out. Even then a pin ma snap but in my experience it can be drilled out in situ using a well greased and frequently wiped and re-greased drill of a suitable size. If the engine does not fire on its first revolution there will be a build up of fuel in the cylinder and exhaust tract that will be evaporated to white fumes when the engine fires.

 

I suspect Richard T's smoke is caused by a somewhat oversized prop holding the engine revs down so the governor goes to full or even excess fuel whilst trying to accelerate the engine and prop. In my view not worth worrying about if the boat otherwise performs well.

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2 hours ago, Traveller said:

Thank Guys.

Tony it is a 1.5, apologies for the omission. The smoke when reving aggressively - effectively slamming the accelerator open - happens when in neutral as well.

Originally you said " get white smoke at start but it ceases very quickly and the engine runs clean. Starting is brilliant in the warmer months, although it can struggle a bit in the colder months. It is only on extremely cold days that it can be a bit of a pig but again it starts and the white smoke clears quickly" That is the bit I was answering. If you are sure it is white smoke when accelerating aggressively the I would suggest (as someone else mentions) it may be timing. The DPA pump has an automatic advance & retard mechanism to aid cold starting etc. so if the basic pump timing is correct then that may be the problem. The 1.5 also has a oil jet to lubricate the pump drive skew gears. If the jet or it associated strainer is blocked then the gears wear and that retards the timing.

 

The jet and strainer are located below the back of the exhaust manifold screwed into the side of the block. One hexagon is horizontal and one close by is vertical.

 

To reset or check  the timing pointer on the pump mounting flange you really need a special tool but I think may engineers nowadays do it by ear, smoke and performance.

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The special tool for timing is fine on a vehicle but almost unusable in a boat unless there  is considerable room like in a wide boat. Especially true with 1.8D

Retard till there is white smoke, advance till it stops + about 1/4" on the scale. 

Take it cruising, try more advance when fully hot. If it makes little difference to the power leave it where it is. Check it starts easily.

Seems to work usually.

Edited by Boater Sam
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  • Greenie 1
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13 hours ago, Tony Brooks said:

 

 

I suspect Richard T's smoke is caused by a somewhat oversized prop holding the engine revs down so the governor goes to full or even excess fuel whilst trying to accelerate the engine and prop. In my view not worth worrying about if the boat otherwise performs well.

Tony, Thanks for your comment.  I'm not at all bothered by the black smoke when revved hard. The boat generally handles well and copes with varaiable conditions on the Soar and Trent. I will not be thinking about changing the prop. If and when the engine needs changing I will see what the manufacturer suggests for prop sizing. Our BMC is coupled to a PRM 260  gearbox which seems to be an almost bomb proof combination.

All the best

Richard

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16 hours ago, Boater Sam said:

The special tool for timing is fine on a vehicle but almost unusable in a boat unless there  is considerable room like in a wide boat. Especially true with 1.8D

Retard till there is white smoke, advance till it stops + about 1/4" on the scale. 

Take it cruising, try more advance when fully hot. If it makes little difference to the power leave it where it is. Check it starts easily.

Seems to work usually.

Sam, I dn't know what tool you have in mind. The ones I used  were smaller than the DPA pump and fitted into the pump drive. I know I used then on cruisers but even with the sound proof box around the Bukh I think I could still easily get them into the engine (not that I need to, I need a wretched dial gauge in the end of the pump).

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