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Old 09-12-2015, 16:36   #1
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Bukh DV20 Cold Start - Any Suggestions?

We have restored a 1975 Bristol 35 equipped with a Bukh DV20. This little engine runs great once started. I have adjusted the decompression lever and valves, installed a new starter, verified batter voltage, added octane boost to diesel fuel, all of which still results in significant cranking to get her going. Once she warms up, she starts first rotation. I am being told a cold start kit would solve this problem, however I have just been advised Bukh no longer makes one. Any suggestions or recommendations?
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Old 09-12-2015, 16:52   #2
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Re: Bukh DV20 Cold Start - Any Suggestions?

Exactly what temperatures are you referring to a "cold start"?

If the ambient is say 60 F or higher, I would expect it to start within a few revolutions when cold and if it is doesn't I would suggest the compression is getting low. Maybe not enough to fix but nevertheless a bit low.

If you are talking ambients of say 40 F or lower, then more serious action might be needed. I'm no expert on cold weather starting but any way of heating the engine, especially the combustion chamber helps. Could be as simple as hot air gun, hair dryer or similar directed into the air intake or as complicated as fitting glow plugs (if possible).

I once had a single cylinder Bukh 10 that was soon worn that it couldn't maintain oil pressure and it would take 5 or more seconds to start cold with ambients around 75 F. After a rebuild, it would start in a revolution or two!
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Old 09-12-2015, 17:22   #3
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Re: Bukh Drsssion mthat low compV20 Cold Start - Any Suggestions?

The flywheel is fairly heavy on these so (in my previous boat) it took a few revolutions to spin up to speed.

In your case, I agree that low compression is a likely reason for difficult starting when cold. A workaround is to pull the decompression levers while spinning it, then close them. The additional revs gained under no compression will help a lot.

I found this method successful when the starting battery was low.
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Old 09-12-2015, 17:29   #4
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Re: Bukh DV20 Cold Start - Any Suggestions?

It would probably be easy to install a heater from a Perkins for example. You already have a hole in your manifold somewhere.
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Old 09-12-2015, 18:36   #5
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Re: Bukh DV20 Cold Start - Any Suggestions?

Once DV20 compression drops 10% plus they will become difficult to start. IF valve lash clearances have been neglected valve regression will be the culprit, a well known source of DV 20 starting issues.
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Old 09-12-2015, 18:55   #6
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Re: Bukh DV20 Cold Start - Any Suggestions?

My DV20 also took a few tens of seconds to start when cold. I installed a cold start kit (Lucas Thermostart), but it didn't make a big difference. I found the best cold start aide was to open the decompression lever, spin up the engine, and then close it. The engine would start instantly. A remote control cable to the decompression lever would allow you to accomplish this from the helm.
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Old 10-12-2015, 12:15   #7
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Re: Bukh DV20 Cold Start - Any Suggestions?

Sounds like the ol' compression may be getting marginal. Your ambient temp is about the same as ours just now, so can empathizes with you..
1) Cranking speed is critical in this weather; use a muti-grade oil, such as 15W 40, to reduce viscous drag.
2) Heat the air intake with a >1500 watt hair dryer, if you have 120V power available.
You can also get a manifold heater, from your local John Deere dealer, for a Yanmar Compact tractor engine of similar HP. You'll have to make an adapter plate to fit it in between the air cleaner/ silencer (if you have one) and the manifold. Not too difficult, if you're handy with tools and have a bit of electrical skill, to wire it up. They are 12V, and work really well.
3) Simply using the compression release, to get the cranking speed up, will also do the job. (I did this on my old Volvo, and got 5 more years out of it) Eventually, you'll have to rectify the compression situation though.
Hope that helps; let me know if you need more info.
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Old 10-12-2015, 17:32   #8
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Re: Bukh DV20 Cold Start - Any Suggestions?

You are not alone!

My old DV20 is getting harder to start, and when dead cold (like, has sat for 3 weeks or more at the dock in BC winter temps) I sometimes have to crank for 15 sec or more (yikes). One cylinder comes in far later than the other, too; the good one catches after maybe 5 sec of cranking and the engine limps along on 1 until the other catches up, many seconds later.

I am now trying to figure out whether this is a fuel issue or whether the compression is getting feeble. If it's the compression then I'm afraid that's the end for this engine... getting too expensive to rebuild Bukhs these days, out here on the West Coast of Canada anyway.

So my solution to this problem at present is to go engine shopping and save up my nickels for a repower (sigh).
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Old 10-12-2015, 17:54   #9
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Re: Bukh DV20 Cold Start - Any Suggestions?

I've seen that junk, at anchor in Nanaimo, I think. Nice boat!
Anyway, if you're mechanically inclined, you may get away with honing the bores and fitting new rings. I've done that on a few engines. It won't last as long as a new one but it'll give you about half the life of new, depending on the wear (both ovality and taper) in the bores, you can measure those easy enough.
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Old 10-12-2015, 19:15   #10
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Re: Bukh DV20 Cold Start - Any Suggestions?

Quote:
Originally Posted by 01kiwijohn View Post
I've seen that junk, at anchor in Nanaimo, I think. Nice boat!
Thanks -- you're remembering Taz, my old boat. She was anchored for years at the end of C-dock at Newcastle Marina/Boatyard in Nanaimo, very visible from the channel. Lovely "galleon" stern on display.

She then moved up to Desolation Sound with me, but I sold her a couple of years ago to some younger, stronger folks from Saturna (I was getting too old to singlehand a hard-mouthed 3-masted 40-footer). The West Coast being what it is, she has now migrated back up to my home port (Cortes Island) so I get to see her often, in her new spiffy coat of forest-green hull paint, and chat with her charming, energetic young owners.

I bought an old beater Contessa 32 (Tazling, i.e. "little Taz") which I've been foolishly throwing money at ever since. Didn't love the boat all that well at first, used to miss the old monster sadly, but the CO32's fine sailing qualities have won my heart and I'm quite attached now. I think I can singlehand this one well into my 60's, which are fast approaching :-) but the Bukh engine... I fear it really has to go.
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Old 28-01-2016, 09:56   #11
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Re: Bukh DV20 Cold Start - Any Suggestions?

We have had the same problem with our old, very worn (low compression) 1973 Bukh DV20 this uses a dynastarter for starting so has to use the decompresser on the start panel. Once started though, she will run all day long.

In the original 1973 owners manual it says to use a drop of oil in the inlet manifold to aid cold starting. So now before starting I found that if I remove the air cleaner and use no more than one squirt of engine oil from a oil can into each cylinder. I then decompress and crank by hand for about 10 revoloutions to spread the oil, while doing this you should hear both the injectors click (mine may need a few more than 10 revs to get both injectors working after few weeks without use) . I then use the starter and decompresser to to get up to speed then release the decompresser and away she goes. Do not use to much oil or you could cause an hydraulic lock and may damage the engine.

I have used this procedure over the past few months and she always starts after a couple of revs after the decompresser is relased and then starts normaly until really cold.

The coldest start here was at -1 deg C air temp.

There are cold start devices online in the UK but not cheap.

Hope this may help.
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Old 28-01-2016, 21:38   #12
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Re: Bukh DV20 Cold Start - Any Suggestions?

My Yanmar 3GN30F starts fine normally when it's above 55 degrees F outside, but will not quite start when it's colder. To start it, I put the throttle down halfway, then push the starter button. It starts immediately. I have to keep my hand on the throttle and back it off to idle immediately, or it'll race.

When it's colder I have to put the throttle all the way down.
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Old 28-01-2016, 22:39   #13
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Re: Bukh DV20 Cold Start - Any Suggestions?



Problem solved!
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Old 29-01-2016, 01:17   #14
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Re: Bukh DV20 Cold Start - Any Suggestions?

FWIW my DVm 24 starts within a 2-3 seconds max. I am not mechanic, but happy to share that comparison if it helps.
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Old 29-01-2016, 11:06   #15
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Re: Bukh DV20 Cold Start - Any Suggestions?

1) At rest, the rack, in the pump, goes to full fuel, so it should fire but at lower temps you have to open the throttle more to keep it running.
2) Check the cranking speed. May need a new ground brush in the starter, and clean up the commutator while you're on the job.
3) At even lower temps, use a hair dryer to heat the intake air. Mine starts at below freezing with this method.
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