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Post by JohnV on Nov 28, 2016 8:26:38 GMT
My mates Gaffer (Beagle of Leigh) has a BUKH 2 cyl engine (of uncertain vintage) which seems to have enormous flow in the diesel return pipe.
My knowledge of diesels is fairly limited but I always understood that a high bypass flow was a symptom of injectors on their way out, however a member of that yacht club told my mate that BUKH engines always did this ........ Being a suspicious old bastard, who always distrusts the wisdom of such self professed "experts", I am now looking for a second (or third or fourth) opinion
Cheers John
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Post by tonyqj on Nov 28, 2016 9:03:16 GMT
I have no specific knowledge of Bukh engines, but a substantial flow in the return could simply be indicative of an over-enthusiastic injector pump.
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Post by TonyDunkley on Nov 28, 2016 10:02:45 GMT
My mates Gaffer (Beagle of Leigh) has a BUKH 2 cyl engine (of uncertain vintage) which seems to have enormous flow in the diesel return pipe. My knowledge of diesels is fairly limited but I always understood that a high bypass flow was a symptom of injectors on their way out, however a member of that yacht club told my mate that BUKH engines always did this ........ Being a suspicious old bastard, who always distrusts the wisdom of such self professed "experts", I am now looking for a second (or third or fourth) opinion Cheers John More info. needed before an answer can be given for this, John. A photo, or photo's, showing the entire fuel system from tank to injectors would be best of all, with a sketch of all the pipe runs coming second best, and failing that a description of the system, along with best estimate of how much fuel is being returned to tank, and in what period of time. If the engine isn't exhibiting any of the usual signs of injectors in need of attention, ie. more reluctant to start than it used to be, accompanied by initial rough running and grey-ish smoke, and /or black smoke at high rpm off load, then it's probably down to an intentional constant partial fuel bleed-off from the top of the secondary fuel filter back to tank sharing the return pipe carrying the leak-off from the injectors.
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Post by JohnV on Nov 28, 2016 10:19:59 GMT
My mates Gaffer (Beagle of Leigh) has a BUKH 2 cyl engine (of uncertain vintage) which seems to have enormous flow in the diesel return pipe. My knowledge of diesels is fairly limited but I always understood that a high bypass flow was a symptom of injectors on their way out, however a member of that yacht club told my mate that BUKH engines always did this ........ Being a suspicious old bastard, who always distrusts the wisdom of such self professed "experts", I am now looking for a second (or third or fourth) opinion Cheers John More info. needed before an answer can be given for this, John. A photo, or photo's, showing the entire fuel system from tank to injectors would be best of all, with a sketch of all the pipe runs coming second best, and failing that a description of the system, along with best estimate of how much fuel is being returned to tank, and in what period of time. If the engine isn't exhibiting any of the usual signs of injectors in need of attention, ie. more reluctant to start than it used to be, accompanied by initial rough running and grey-ish smoke, and /or black smoke at high rpm off load, then it's probably down to an intentional constant partial fuel bleed-off from the top of the secondary fuel filter back to tank sharing the return pipe carrying the leak-off from the injectors. Thanks Tony ....... The engine starts/runs very nicely with no noticeable smoke, little bit of black smoke if you whack open throttle when in gear but clears straight away. So no sign of poor spray pattern etc. Next time I'm on his boat I will try and get a proper estimate of fuel return but it was pretty hefty. We had a problem with a blocked fuel pickup pipe inside the tank. (as usually happens at a tricky moment threading between lines of moorings nose into the wind and and tide) We were using a big pickle jar full of diesel to feed the engine to get us back to the mooring, at tickover it almost emptied the jar in less than a minute. Desperate times .... desperate measures ... A pair of mole grips pinching the return fuel line stopped (or reduced) the flow and the jar of diesel took us easily the few miles back up the river to our mooring ..... probably not using more than a cupful. It was just the rate that it drank the jar full initially that started alarm bells ringing
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Post by Telemachus on Nov 28, 2016 10:50:43 GMT
Beta engines have a substantial flow through the whole injector system, they are designed that way and one up-side is that any air is automatically pushed through the injector pump. I've no idea whether Bukhs are the same but its certainly not necessarily indicative of any problem.
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Post by TonyDunkley on Nov 28, 2016 10:57:32 GMT
More info. needed before an answer can be given for this, John. A photo, or photo's, showing the entire fuel system from tank to injectors would be best of all, with a sketch of all the pipe runs coming second best, and failing that a description of the system, along with best estimate of how much fuel is being returned to tank, and in what period of time. If the engine isn't exhibiting any of the usual signs of injectors in need of attention, ie. more reluctant to start than it used to be, accompanied by initial rough running and grey-ish smoke, and /or black smoke at high rpm off load, then it's probably down to an intentional constant partial fuel bleed-off from the top of the secondary fuel filter back to tank sharing the return pipe carrying the leak-off from the injectors. Thanks Tony ....... The engine starts/runs very nicely with no noticeable smoke, little bit of black smoke if you whack open throttle when in gear but clears straight away. So no sign of poor spray pattern etc. Next time I'm on his boat I will try and get a proper estimate of fuel return but it was pretty hefty. We had a problem with a blocked fuel pickup pipe inside the tank. (as usually happens at a tricky moment threading between lines of moorings nose into the wind and and tide) We were using a big pickle jar full of diesel to feed the engine to get us back to the mooring, at tickover it almost emptied the jar in less than a minute. Desperate times .... desperate measures ... A pair of mole grips pinching the return fuel line stopped (or reduced) the flow and the jar of diesel took us easily the few miles back up the river to our mooring ..... probably not using more than a cupful. It was just the rate that it drank the jar full initially that started alarm bells ringing That's enough info. to be able to rule out any injector problems being the cause of the high rate of fuel return to tank. If the engine is fitted with a lift pump drawing fuel from a dip-tube through the top of the tank, and the fuel piping on the engine is still standard and hasn't been modified, then a rate of return to tank equal to or greater than the rate of fuel consumption is perfectly normal, . . . it's simply done to prevent any air that may get drawn into the system on the tank [suction] side of the lift pump reaching the injector pump(s) and injectors by bleeding off a good proportion of what the lift pump delivers from the top of the last filter on the engine [pressure/delivery] side of the lift pump and sending it back to the tank along with any entrained air which would otherwise build up in the top of the filter and then cause the engine to misfire or conk out. To simplify and minimize the piping, the leak-off from the injectors is connected to the engine end of the return line, instead of being run in a separate pipe back to the tank.
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Post by JohnV on Nov 28, 2016 11:44:42 GMT
Thanks Tony ....... The engine starts/runs very nicely with no noticeable smoke, little bit of black smoke if you whack open throttle when in gear but clears straight away. So no sign of poor spray pattern etc. Next time I'm on his boat I will try and get a proper estimate of fuel return but it was pretty hefty. We had a problem with a blocked fuel pickup pipe inside the tank. (as usually happens at a tricky moment threading between lines of moorings nose into the wind and and tide) We were using a big pickle jar full of diesel to feed the engine to get us back to the mooring, at tickover it almost emptied the jar in less than a minute. Desperate times .... desperate measures ... A pair of mole grips pinching the return fuel line stopped (or reduced) the flow and the jar of diesel took us easily the few miles back up the river to our mooring ..... probably not using more than a cupful. It was just the rate that it drank the jar full initially that started alarm bells ringing That's enough info. to be able to rule out any injector problems being the cause of the high rate of fuel return to tank. If the engine is fitted with a lift pump drawing fuel from a dip-tube through the top of the tank, and the fuel piping on the engine is still standard and hasn't been modified, then a rate of return to tank equal to or greater than the rate of fuel consumption is perfectly normal, . . . it's simply done to prevent any air that may get drawn into the system on the tank [suction] side of the lift pump reaching the injector pump(s) and injectors by bleeding off a good proportion of what the lift pump delivers from the top of the last filter on the engine [pressure/delivery] side of the lift pump and sending it back to the tank along with any entrained air which would otherwise build up in the top of the filter and then cause the engine to misfire or conk out. To simplify and minimize the piping, the leak-off from the injectors is connected to the engine end of the return line, instead of being run in a separate pipe back to the tank. Thanks for that Tony, A nice clear explanation, easily understandable. (even by the mechanically challenged ) As I said, my knowledge of diesel engines is fairly limited and the ins and outs of fuel delivery systems is well outside my comfort zone. (My engine repair experience is limited to the art of keeping elderly and abused motorcycles alive)
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Post by Deleted on Nov 28, 2016 12:28:31 GMT
Have you got the instruction Bukh
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Post by Deleted on Nov 28, 2016 12:31:48 GMT
One of my generators has a little Kubota engine in it with electric pump which pumps fuel through the filter straight to the leak off as soon as the ignition/fuel pump is switched on. You stop the engine by turning the fuel pump off.
I had to wire up my own start panel and I was a bit confused by the fuel just going round in a loop back to the tank but as telly said it is self bleeding like that which is sensible. Injector pump just takes what it needs from the constant supply.
Main engine is a Beta 90 Kubota engine but has a mechanical lift pump and a primer on the fuel filter so I think its a different setup.
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Post by naughtyfox on Nov 28, 2016 15:30:39 GMT
Foxy reading this... at 1730 Athens time (we're on the same longitude)... stand by for edit.... Here's the manual pdf for starters: www.boatservicehaarlem.nl/bukh_dv10_dv20_workshop_manual.pdfI would first ask the usual - age of engine, engine history/service history/abuse/modifications - what spare parts and when, previous problems... Why was the fuel pick-up pipe blocked? Is the bottom of the tank clean? Has the fuel been filtered/'polished'? I can't better Mr Dunkley's words. You can sift through the workshop manual, or how about giving T W Marine a phone call? They're nice guys (Nick & Steve) and I'm sure will happily and patiently answer such a question. "My mate's Gaffer (Beagle of Leigh) has a BUKH 2 cyl engine (of uncertain vintage)" - engine number and contact Bukh for age. (oh, and apostrophe inserted!)
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Post by naughtyfox on Nov 28, 2016 15:50:49 GMT
Should have started straight away, and NOT good to rev it up cold. By the way, in the Bukh DV20 both pistons go up and down at the same time:
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Post by naughtyfox on Nov 28, 2016 15:53:02 GMT
Go to 1:00 for the start of engine:
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Post by naughtyfox on Nov 28, 2016 15:59:30 GMT
Here's the DV10, what we have:
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Post by bargemast on Nov 28, 2016 17:14:01 GMT
Should have started straight away, and NOT good to rev it up cold. By the way, in the Bukh DV20 both cylinders go up and down at the same time: There must be something seriously wrong with the Bukh engine if both cylinders go up and down at the same time.
You surely wanted to write that both pistons are going up and down at the same time, which is how it should be on the Bukh twin . Peter.
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Post by naughtyfox on Nov 28, 2016 17:24:04 GMT
"You surely wanted to write that both pistons are going up and down at the same time, which is how it should be on the Bukh twin." Indeed I did, and now edited to correct that. Thanking ye
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