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

does it start quickly without a lot of cranking?

Starts perfect within 5 seconds every time.

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.

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.

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

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.

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!


Bill

WilliamR said:

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

Click to expand...

Been there

Oil Pan Capacities for Cummins Marine Engines - Seaboard Marine

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.

Don't be nervous, 13 quarts is still lots of oil and will reduce the splashing at the rear cylinders.

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.

Ski in NC said:

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.

Click to expand...

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.

Thanks. Will definitely try a lower oil level. I also wondered if valve seal wear normally an issue at 2000 hrs?


Bill

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.

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.


Bill

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.

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.

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: Dropbox - File Deleted - Simplify your life
Looks like I need an engine specialist to take a look. Anyone know a good one near Vancouver BC?

Bill

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

Slow starting can be caused by low batteries. If batts. are weak or there are poor connections the cranking will be slower which means tougher starting. This may not be noticed in warmer weather. Unless you are quite familiar with the cranking performance you may not even be aware if it is slow.

Check all connections, clean them and ensure they are tight.

Cold batteries do not put out as much power as warmer batteries. If the batts. are old or inadequate they may simply not be able to produce sufficient power to spin that engine for a REAL cold start..

Check the at rest battery voltage. should be 12.6 or so. NO CHARGER.
Check the cranking voltage at the battery. Should not drop more than 0.5V
Check the cranking voltage AT THE STARTER. Should not drop below ~10.5 v under cranking conditions.
Can't give you exact but these are reasonable guides.

If those conditions are failed then more investigation will be required but that can cause slow cranking and the resulting tough starts.

The longer the cranking goes on the more fuel is put through the engine into the exhaust system which will then produce more than normal smoke plus cold combustion chambers do not burn fuel well.

Before starting all lines, power cable should be off with the exception of only those needed to prevent the boat from drifting away. All crew aboard except only those needed for handling the remaining lines. Start up, wait a few seconds for the engine to stabilize and go. Just a light load as you leave the marina and then once clear run it a bit faster and it should clear fairly quickly.

Tony Athens said:

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 started 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

Click to expand...

Many thanks for the input and so answers in sequence:

1) There are 2 small electric air heaters in the boat on constantly to stave off freezing over winter. One is in the engine room. There is a block heater power cord that comes off the rear of the engine under the oil cooler. I plug that in for 1/2 hour before start up. It came with the boat, and looks internal Cummins one, as there is no heater pad on the oil pan. I run the engine normally for 5 mins at the dock before moving off.

2) Yes, currently been doing that monthly over winter, just to circulate the oil.

3) Since we last did a trip (end of sept)that would be 5 times in total, twice this month.

4) Temps have always been good and stable. Never got overheated. Checked the water pump this fall and just had the heat-exchanger serviced. Cruises at 190 @ 2000 rpm if I recall. About 5 degrees lower at idle I think. I'd have to check my logbook but I haven't seen it get above that.

5) It has always started with manual pre-heat on for 20-30 seconds in about 5 seconds flat. The previous owner had beefed up the starter battery bank, so the starter cranks very well. Today weirdly it took two times to get started. Firstly wouldn't catch on first try for 20 secs, then secondly started rough after a second 20 second crank. Ran rough for a bit then smoothed out. Lots of smoke evident.

6) Cummins Quick Serv for my engine: Service Manual for B5.9 in the section 014-008 Engine Testing (In Chassis) states:


7) See item 1 response. Thats a shame. I always hoped it would help a bit. I hear it make a hissing noise and see the voltage drop when its on. It uses 120v.

8) No correspondence to note, but pic and videos attached. I'll try and get some more when I am at the boat next.

Thanks
Bill

Your engine compression test results are well outside the Cummins psi specs you quote, ie. "All cylinders must be within 690 kPa [100 psi] of each other.".

BruceK said:

Your engine compression test results are well outside the Cummins psi specs you quote, ie. "All cylinders must be within 690 kPa [100 psi] of each other.".

Click to expand...

His max difference is 40psi. That's less than 100, right? Or maybe we are reading it differently?

twistedtree said:

His max difference is 40psi. That's less than 100, right? Or maybe we are reading it differently?

Click to expand...

You are right, I plead "senior moment". (But, we were polite about it.)
Apologies to the OP for my error.(Humility on display too).

My brand new Cummins Reman engines smoke a bit on startup, at least for the first few minutes. Actually every diesel engine I've ever seen, at least in our lattitude smokes a bit for the first few minutes.

I'm not sure you actually have a problem.

Considering answers 2 & 3 picture 1 and the season I would say that smoke at startup to be expected. But it is just a thought coming out from a sick mind so let's wait answer from our expert Tony

When hooked up from factory those intake air heaters cycle on and off continuously when engine is cold. Even if it cools way down after a run they start working again. They are not glow plugs as you seem to be operating them,only briefly before cranking.

You are in Canada with very cold air and very cold water throough the aftercooler. How did it work in summer??????

bayview said:

When hooked up from factory those intake air heaters cycle on and off continuously when engine is cold. Even if it cools way down after a run they start working again. They are not glow plugs as you seem to be operating them,only briefly before cranking.

You are in Canada with very cold air and very cold water throough the aftercooler. How did it work in summer??????

Click to expand...

Thanks. Pretty sure I don't have intake air heaters, as it's just a power cord that goes into the block. Not entirely sure where it is located though. the external anti-frost heaters are just the standard Westmarine round ones. It is about -5 centigrade here currently, and it was starting fine in the summer, but smoked a bit on start up - no where near this amount though.

Not sure this is relevant...and I don't think it is, but that exhaust pipe is tiny. What size engine is this...HP rating???