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Old 02-01-2017, 01:28 PM   #1
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Blue smoke on start up: 6BTA

Hello,

I have a 2000 Nordic Tug 32 with a Cummins 6BTA engine with 2000 hrs on it. We bought the boat last year and the survey was fine, except the aftercooler needed a service as was leaking (there was sodium in the oil analysis). That has now been fixed.

It runs great, and drives the boat at advertised speed, but we notice clouds of blue smoke on start up, that clear after about 15 minutes, Naturally, being concerned at this sign of oil being burned we have checked out the compression, turbo and exhaust, but all are seem in good shape. We even installed new injectors and a Tony Athen's Envirovent system at the end of the year. Compression recorded was:

1) 315
2) 300
3) 340
4) 340
5) 335
6) 310

Oil filter is clean when inspected and last oil analysis showed all items returning to normal ranges. So, I am wondering what most likely causes are. I would have thought a major problem like stuck rings or cylinder problems would have given more symptoms. I wondered about checking the valve seals/guides next, and if this is a job you can do in situ, or if the head needs to come off for that.

Any thoughts on my predicament gratefully received!

Bill
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Old 02-01-2017, 01:41 PM   #2
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does it start quickly without a lot of cranking?
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Old 02-01-2017, 01:51 PM   #3
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Starts perfect within 5 seconds every time.
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Old 02-01-2017, 02:08 PM   #4
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Does the Envirovent system return oil vapor to the intake? I don't know anything about the system. Maybe its the cause before warm up.
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Old 02-01-2017, 02:12 PM   #5
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is the manifold heat system working? you can usually tell because the voltage will drop for a brief period then recover as the heater switches on and off.

It is not necessary nor helpful to have a long warm up period as the engine won't really warm unless loaded.
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Old 02-01-2017, 02:14 PM   #6
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Thanks.


Preheat is manual and we get a big voltage drop when it kicks in and I usually leave it for at least 20 seconds. I also have a block heater I usually put on for 20 mins before start.


It was doing this before the Envirovent system was fitted (the reason we installed it). The crankcase vent for that is at the front of the engine, and it works fine (previously had a Walker AirSep). Some folks have suggested not filling the oil level to the top mark on the dipstick, as the engine is installed at a down angle, so might try that also.


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Old 02-01-2017, 02:17 PM   #7
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Did it smoke before you added the system??

Be sure the lube oil is not too high. Many engines are at such an angle that the oil needs to be a few quarts lower.

My engines would use oil until they got 2 qts low then oil use stopped.
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Old 02-01-2017, 02:19 PM   #8
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Thanks Bayview, yes it did smoke before (see above response). I might try running with oil at the lower mark, but am a tad nervous about that!


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Old 02-01-2017, 02:19 PM   #9
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Quote:
Originally Posted by WilliamR View Post
Thanks.


Preheat is manual and we get a big voltage drop when it kicks in and I usually leave it for at least 20 seconds. I also have a block heater I usually put on for 20 mins before start.


It was doing this before the Envirovent system was fitted (the reason we installed it). The crankcase vent for that is at the front of the engine, and it works fine (previously had a Walker AirSep). Some folks have suggested not filling the oil level to the top mark on the dipstick, as the engine is installed at a down angle, so might try that also.


Bill

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Old 02-01-2017, 02:22 PM   #10
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Hmmmm. Are you sure it is blue smoke and not white smoke that is very common on engine start up with a cold engine???? My 330B's smoke like crazy if it is cold out. But it clears up very quickly.
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Old 02-01-2017, 02:24 PM   #11
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Don't be nervous, 13 quarts is still lots of oil and will reduce the splashing at the rear cylinders.
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Old 02-01-2017, 02:28 PM   #12
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Blue smoke on 6BTA cold start is partially burnt fuel and has nothing to do with lube oil. Seems like you took a hit on compression from the aftercooler failure. That could have corroded cylinder walls or valves. Lower compression makes cold smoke worse.

Probably ok to just live with it.

Check blowby for puffing at hot idle.
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Old 02-01-2017, 02:42 PM   #13
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Quote:
Originally Posted by Ski in NC View Post
Blue smoke on 6BTA cold start is partially burnt fuel and has nothing to do with lube oil. Seems like you took a hit on compression from the aftercooler failure. That could have corroded cylinder walls or valves. Lower compression makes cold smoke worse.

Probably ok to just live with it.

Check blowby for puffing at hot idle.
Cummins manual puts those compression ratings as normal for an older engine, so I was not too concerned with cylinder valve corrosion. Blowby doesn't seem an issue, but not sure how to check, other than the teakettle test (which I have done) which was OK.
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Old 02-01-2017, 02:44 PM   #14
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Thanks. Will definitely try a lower oil level. I also wondered if valve seal wear normally an issue at 2000 hrs?


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Old 02-01-2017, 02:47 PM   #15
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With engine hot and idling at dead slow, take oil filler cap off and watch flow with flashlight. Should just be a gentle stream of vapor wafting out. If it puffs in sync with one cylinder firing, that is an issue.
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Old 02-01-2017, 02:50 PM   #16
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Done that in the dock, and to see if the cap vibrated lots with when placed on the filler opening (tea kettle test). It didn't, but will try when idling under way.


Wouldn't I see more of a problem in compression readings if that were the case though? Those readings were in the normal range given by Cummins. #2 was lowest, but still in range.


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Old 02-01-2017, 03:13 PM   #17
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Comp readings vary more than normal, but I would not worry too much about it. I have dealt with a few engines with high blowby and varied compression and the recommendation was to just run it and smile. None actually failed, but they were run easy afterward.
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Old 02-01-2017, 07:33 PM   #18
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Do you start, throw off the ropes and go or do you idle at the dock until warm? It takes much longer to warm at the dock and may not even reach operating temps at the dock. Warm it up under a load.
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Old 02-01-2017, 08:28 PM   #19
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Ok, went down this PM and the engine actually took quite a bit of coaxing to start today and the smoke was even worse! I took some photos and a video (but don't think I can post that).

See: https://www.dropbox.com/s/npvtf1xtk6...5.30.jpeg?dl=0
Looks like I need an engine specialist to take a look. Anyone know a good one near Vancouver BC?

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Old 02-01-2017, 10:23 PM   #20
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Bill,

I've been watching this & so far all of the questions have be right.. But let's take a deep breath and start fresh although I may cover what has already been asked but maybe in a different way so I can get a better feel for what is going on…………………..OK??

1) Current operation.. Do you try and warm your engine at the dock? If so, tell me what your typical protocol is?

2) When you go down to your boat, do you ever start the engine without leaving the dock and taking the boat out on a voyage?

3) Since the last time you actually left the dock to go “someplace”, how many times have you stated the engine? Think about it and be pretty accurate over the past year?

4) When you are out on a trip, have you noticed your coolant temps after the engine is up to to running temps? Like maybe 185-195F at cruise RPM’s and something less when idling? Give me some numbers and RPM’s..


5) Are you saying that it takes about 5 seconds of cranking to start the engine and that has always been the case, or has that 5 seconds “grown” since when you bought the boat?

6) can you show me exactly where you came up with those "compression specs" that you quotes came from Cummins? "Cummins manual puts those compression ratings as normal for an older engine"


7) An FYI, turning on your block heater ( not sure what you actually have but would like to know what you have) would typically do NOTHING if not on for the previous 24-48 hours.

8) And last--do we have any emails between us early on when you were thinking about getting an Envirovent , etc, etc?? If send send me the string.

Let’s start there plus one more thing.. I’d like to see good pics of your engine as installed in the boat showing all from all angles & perspectives—All must be clear & in-focus.. You can post here, but best to send them to me direct at tony@sbmar.com..
I'll put the time in to help but you have to put your time in to help me help you.. 8 questions and need 8 good answers to get started..



Tony
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