Sluggish Bukh

mick

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Today in the boatyard my Bukh 10hp was hard to start, eventually caught but soon died. After two or three goes it kept running, but very slowly, and would not answer the throttle. After a couple of minutes of this it ran normally, throttle and all. Very cold weather today here in West of Scotland, could the answer be as simple as that? I am strictly a fair-weather sailor.
 

castaway

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I had a Sabb 8hp which had similar symptoms, after checking all the obvious things like compression injector etc. it turned out to be a choked up exhust silencer. On the Sabb it has a big cast iron thing on the side of the block on mine a combination of rust and coke had constricted it... came on quite suddenly as well.

Nick

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MarkJohnson12345

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I agree with you about cold weather. Our old Bukh 20 and the 10 before that are not brilliant at starting in very cold weather. Even difficult to start in cold weather.

I used to start the old Bukh 10 with a small sniff of easy start. People don't recommend it but it did help to start the old thing.

There are some 'wives tales' on how to help start an old diesel, like holding a burning bit of paper by the air intake whilst starting.

If you have three hands you could try this method!

If the engine is 100 % ie good compression etc, it will start as you did, after three or four tries. Just keep a good battery on board.

If the engine is old and worn, wait til summer.

In the antartic, they leave diesels running for 6 months..................
 

cliff

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1) Tick over set too low,
2) spring missing from governor return (unlikely),
3) sticking governor

Most likely 1) and / or 3)

The throttle does not actually operate the governor but rather it moves a "stop" which the governor runs against. Give the engine a run and when the throttle "works" rev her up and down to operate the governor and get some oil thrown round it.

After a short run stop the engine and restart and see what happens.
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jerryat

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Hi asj1,

As you say, there are no special starting arrangements as standard, though you can retro fit a heating coil to the inlet manifold that preheats the incoming air and makes starting considerably easier, though have only used it about 3 times in 16 years on my boat. Never have probs starting in very cold weather.

I'd go with checking the exhaust elbow then fuel filter(s) as has been suggested, but could the residual water in the exhaust system have been frozen?? If so, the motor might (just) start but not be able to push enough air through the exhaust until it had melted a bit. Would tie in with the fact that it ran fine later.

I doubt really if the exhaust elbow is the culprit since the motor apparently runs ok after a few minutes. It almost sounds as if the governer control was sticking (perhaps due to the very cold weather as the engine didn't respond to the throttle at first. Were the batteries flattish? If so, when the motor did start, albiet sluggishly, the alternator would be attempting to put a lot into the battery bank and causing quite a load on a small engine to start with.

Or, as mick hopes(!) perhaps it's simply the rotten weather! Hope so.

Cheers Jerry
 

oldharry

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Quite like the idea of ice in the exhaust pipe! But I think it more likely the filter(s) are on the way out. if you have just replaced them, then there could well be a small air leak, or maybe the system needed a bit more bleeding.

The symptoms you describe suggest very strongly insufficient fuel was reaching the engine, either because of blockages or air leaks. The Bukh system is quite good at purging itself of air so that it all settles down.

Cold weather? Very very unlikely. It may make initial starting more difficult, but once the thing is firing the speed of the engine will heat the air charge sufficiently on each compression stroke to keep it going provided everything else is working normally and suffient fuel is reaching the injectors.

If it does it again, disconnect the fuel return pipe from the top of the filter and see if there are any bubbles coming out. The problem is that you can get microscopic bubbles that are too small to see, but are enough to upset the injectors, so run a tube into a jamjar from the return feed and see if any air or froth collects when the engine turns over (like bleeding brakes).
 

pappaecho

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Diesel fuel waxes in cold weather - commercial diesel used for lorries and similar has additives to prevent this - in fact I have heard that the fuel pumps sell summer and winter grades of diesel. Could it be that the boat was filled up with summer diesel?
Some months ago, on the forum, an enquirer was asking about petrol contamination with diesel. A reply from Scotland said that commercial fishermen add 5% petrol to the diesel mix to aid starting, and prevent waxing. Old wives tale?
 

oldharry

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[ QUOTE ]
fishermen add 5% petrol to the diesel mix to aid starting, and prevent waxing. Old wives tale?

[/ QUOTE ]

No, used to be common practice not only in commercial boating, but road transport hauliers. Modern diesel fuels have anti waxing additives.

But I dont think waxing is the cause of the problem in this case, because to cure it you have to warm up the fuel in the tank, and the fuel lines before you can get started. I remember seeing pictures in the great 1963 winter of frustrated lorry drivers actually lighting fires under the fuel tanks to try to melt the wax off.....
 

Seal_surfer

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I've had similar symptoms on an old Bukh 10 that were probably due to minor fuel leaks around main filter and lift pump banjo connections. When boat is unattended for longer periods, fuel can weep out, so air gets in. Injector pump can't deliver full pressure/volume until air is purged - either through its clever self-bleeding design or through the injector (hence only just able to run until clear). If you were to prime/bleed using decompressor, you may get through it quicker. Best is to look for leaks using a dry paper towel dabbed around unions and check if damp (starting at highest point).

Is the main fuel filter sealing OK - was it recently changed in servicing?

Good luck.
 

Colvic Watson

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BUKH DV10 cold start procedure is to turn the engine over a few times with the decompression on, then start as normal. Preferred method is to do the first part with the hand start lever.
 
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