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Old 07-25-2011, 09:16 AM   #1
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Our Cummins is sick.......

Hi all. Yesterday*the 330hp 6BTA Cummins in our 2003 Mainship 390 started blowing black smoke and losing power. First time it's ever smoked at all. The engine has 790hrs on it, almost all of it in fresh water.*We were 2hrs out so limped back to the marina, with the engine feeling like it was running on 5cyl. No abnormal temp. or oil pressure readings, or unusual noises.*The oil level, however, is now way up. I think it's likely*fuel contaminated since there's no evidence of water on the dipstick, and coolant level is normal. I have no diesel engine expertise (but lots of hands-on gas engine experience)*and*would like*to establish what has failed before I call in the specialists. I'm hoping someone in the group can comment on my approach to this issue, which I'm hoping is a failed/stuck injector: 1/ Drain oil and check for contaminants, both visually and by smell(presence of fuel).* 2/ change filter and refill with fresh oil. 3/ Restart and "crack" injector supply lines to try and identify bad cyl.(read about that technique on Boatdiesel forum)*4/ Remove injector and inspect/clean/get pressure tested (I believe any diesel shop can do this?) 5/ Inspect the suspect cyl. with a borescope. 6/ Pray!

There was no evidence of unusual blowby, I'll check into that more when I go back to the boat. I added a "puke bottle" to the crankcase vent in the spring so the evidence should be in there.

Needless to say this is a very troubling development and totally unexpected......the engine has been maintained to Cummins standards, the boat is propped correctly and fuel properly filtered (Racor 2micron), and stabilised during off-season. It always starts instantly and has run flawlessly up to now.

As I stated before I have no hands-on diesel experience, but I am hoping to learn real fast! Any tips/guidance from those with more experience in "the holy place" on their boats would be greatly appreciated.

Thanks',

Nick

*
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Old 07-25-2011, 09:29 AM   #2
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RE: Our Cummins is sick.......

If you recently added a "puke Bottle" have you run much since doing that? Maybe that installation has something to do with the problem?
How about the air intake or filter, I have never seen it on a boat but tractor diesels will send out black smoke when the air filter is plugged up.
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Old 07-25-2011, 09:42 AM   #3
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RE: Our Cummins is sick.......

I've probably put about 10hrs on since adding the catch bottle to the crankcase vent. It is still vented with the same diameter hose, which now goes in/out of a small plastic gas can to eliminate the drips. This shouldn't cause any backpressure, but I'll double-check the installation, just to be sure. Thx.
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Old 07-25-2011, 10:17 AM   #4
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RE: Our Cummins is sick.......

Post your problems with the Cummins experts on boatdiesel. It could be several things, starting with over prop*----- etc. Any chance of seawater getting into engine via exhaust elbow? This has been a weak point on some Mainships.
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Old 07-25-2011, 10:18 AM   #5
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RE: Our Cummins is sick.......

Hi Nick,

The puke bottle should be irrelevant. On my 5.9 I just added a tee in the crankcase vent line and put a bottle at the low point, been like that for years.

Agree it is a fuel issue, whether it is bad fuel or an injection issue, could be the high pressure pump too, hard to say at this point, but you should call a qualified mechanic over for a look see.

good luck
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Old 07-25-2011, 10:57 AM   #6
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RE: Our Cummins is sick.......

Zero chance of water backtracking up the exhaust.....we're on a very placid river here (Rideau) and the boat never gets exposed to waves/wakes whist anchored. But also, the no wake rules*limit the opportunities to "throttle up"*and work the engine harder........I do it when I can, and the stretch in front of our marina is quite wide so I can usually finish a cruise that way, which I understand is a good idea.

Can anyone tell me if special tools are required to remove an injector on a 6BTA?
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Old 07-25-2011, 11:20 AM   #7
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RE: Our Cummins is sick.......

Injectors are not the issue, unless you pumped a bunch of water through due to very bad fuel. They should be good for 6000 + hours.

If your exhaust elbow went bad, it is not difficult to get a back flow of seawater. Expect 5 to 8 years out of an elbow before you give it a good check.

Again, best you repost on boat diesel.

*
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Old 07-25-2011, 12:24 PM   #8
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RE: Our Cummins is sick.......

"Remove injector and inspect/clean/get pressure tested (I believe any diesel shop can do this?)"

Most any diesel INJECTOR shop, not just a general repair place with a toolbox and a set of hammers..

Black exhaust is too much unburned fuel or too little air.

Is the engine turboed? If so I would start there.
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Old 07-25-2011, 12:54 PM   #9
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RE: Our Cummins is sick.......

Quote:
FF wrote:
Is the engine turboed? If so I would start there.

*Yes, it's turboed. Other than a mechanical failure of the turbo what would I look for? If it's dirty in there, how do*I clean it?
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Old 07-25-2011, 01:18 PM   #10
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RE: Our Cummins is sick.......

The very FIRST thing I would look for based on your description is a blown compressed air hose or connection. Follow the air plumbing from the turbocharger output to the intake manifold. Look for a broken hose or more likely a connection where the hose slipped off.

You can clean the compressor side of the turbo easily using brake clean, etc. Put a paper towel or oil diaper under the opening and spray and let the yuck collect in the towel. But if it spins freely and is not hitting the housing you likely don't have a turbo problem.

Injectors are easy to pull on a Cummins 6B if you get to that point. I have done many on trucks. You can do it with a prybar once the fuel lines are out of the way and the retaining nuts are removed. I forget the size of the retaining nut (maybe 24mm). However, as stated with only 800 hours on the engine injectors are not likely the problem unless you have had water in your fuel.

*
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Old 07-25-2011, 01:54 PM   #11
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RE: Our Cummins is sick.......

OK, thank you for the tips, I'll certainly be looking at those areas when I go back to the boat, instead of focussing solely on injector issues. Maybe, as a neophyte diesel owner, I've been swayed by all the hype about fuel additives, injector cleaners etc., assumed the problem was with the injectors,*and have overlooked the possibility that the problem is elsewhere. Kind of like losing one's "situational awareness" during troubleshooting. I'll try and keep a logical, open mind when I go back, except when I'm praying, of course............

*

Nick
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Old 07-25-2011, 07:19 PM   #12
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Our Cummins is sick.......

Quote:
tachyon wrote:
* The oil level, however, is now way up. I think it's likely*fuel contaminated since there's no evidence of water on the dipstick, and coolant level is normal. *
--------------------------------------------------------
I'm not a 6BT mechanic but a*couple of other things to check:
Quote:
(Also does your engine have electronically fired injectors.* If so, a broken wire will cause the engine to misfire on one cylinder.* Volvo is currently going through a recall on bad engine injector wiring harness on several of their engines. *Running them in this manner has caused some severe damage to the pistons.)
From the symptoms you are describing I would also check:
** The engine fuel supply pump for a broken diaphragm.* This will leak fuel oil directly into the crank case. *An overfilled crankcase, specially with diesel oil, will suck oil up into the cylinders and put out a heck of a lot of smoke and will stink to the high heavens.
*** A stuck valve or broken exhaust valve spring will also cause loss of compression and the cylinder not to fire.* Guess where the fuel oil goes that the injector is faithfully pumping into the cylinder?* Right into the crankcase.
***Have you had your valves adjusted lately?* If a pushrod gets bent or too loose and jumps off the rocker, you have the same issue as above, with fuel oil accumulation in the sump and a misfire on that cylinder.
Taking the valve cover off and a visual inspection while rolling the engine over slowly will reveal any issues with the valve train. Look for a loose push rod and rocker not moving.
If you can't find it, don't run the engine under load until it's repaired.
Larry B


-- Edited by Edelweiss on Monday 25th of July 2011 07:31:45 PM
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Old 07-26-2011, 04:29 AM   #13
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RE: Our Cummins is sick.......

Take out the turbo and see if it still spins freely.

I would also look for a leak in the intercooler for a major air leak..

"Maybe, as a neophyte diesel owner, I've been swayed by all the hype about fuel additives, injector cleaners etc., assumed the problem was with the injectors,"

This is because folks are always looking for a quickie solution , and most of these "cures" have an immense markup, needed to pay for the advertising.
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Old 07-26-2011, 05:47 AM   #14
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RE: Our Cummins is sick.......

Take out the turbo and see if it still spins freely.

*

No need to remove the turbo to check for that on this engine.


*
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Old 07-26-2011, 06:04 AM   #15
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RE: Our Cummins is sick.......

I think before yanking injectors, valve covers, and turbos you had should hire a good mechanic, as the owner of a 6BT I'd like to hear what the problem is, please let us know.
Thanks,
Steve W.
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Old 07-26-2011, 06:25 AM   #16
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Our Cummins is sick.......

Quote:
Steve wrote:
I think before yanking injectors, valve covers, and turbos you had should hire a good mechanic, as the owner of a 6BT I'd like to hear what the problem is, please let us know.
Thanks,
Steve W.
*I agree.* Don't jump to conclusions.* A perfectly good running engine for the most part doesn't just blow up.* Stick to the simple stuff first and go from there.* A good technician is in order.* Circuit boards and electronics can reek havoc and without the proper test equipment you are shooting in the dark.


-- Edited by JD on Tuesday 26th of July 2011 06:27:40 AM
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Old 07-26-2011, 07:36 AM   #17
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RE: Our Cummins is sick.......

Thank you all for your responses and words of wisdom. I really appreciate it. There aren't a lot of diesel boats in our area, hence a shortage of local technical help. Our marina does have a diesel specialist it can call in from another town, if required. I intend to look at the basics as you've suggested and just go from there.

This engine issue comes along just after reading an article in the latest Passagemaker about a Cat diesel owners' experience in using*regular oil*analysis to try and*predict engine problems.......a bit of a horror story since he ended up doing a complete rebuild after less than 1600hrs, in spite of high levels of contaminents detected after only 800hrs., and following Cat's advice on what to do about it. Scary stuff.

Nick
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Old 07-26-2011, 07:42 AM   #18
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Our Cummins is sick.......

Nick,
You can take this advice to the bank, and I mean it. Before doing anything else call Tony Athens at Seaboard Marine (sbmar.com to get his number). DO NOT let a mechanic touch your engine until you talk to him. He can be abrasive but he's straight forward and knows more about Cummins engines than anyone else, including probably Cummins themselves. Until you get a handle on things talk only to Tony. He is the most respected moderator on boatdiesel.com


-- Edited by timjet on Tuesday 26th of July 2011 07:45:39 AM
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Old 07-26-2011, 08:53 AM   #19
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RE: Our Cummins is sick.......

Quote:
timjet wrote:Nick,
You can take this advice to the bank, and I mean it. Before doing anything else call Tony Athens at Seaboard Marine (sbmar.com to get his number). DO NOT let a mechanic touch your engine until you talk to him. He can be abrasive but he's straight forward and knows more about Cummins engines than anyone else, including probably Cummins themselves. Until you get a handle on things talk only to Tony. He is the most respected moderator on boatdiesel.com
*Agreed.* Good advise.
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Old 07-26-2011, 03:41 PM   #20
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RE: Our Cummins is sick.......

** I think ileonard is on the right track, the engine is not getting enough air, check the air filter, the complete air system from filter to intake manifold, is the turbo working, do you have a boost gage telling how much boost you have and last but not least is the blow off valve stuck open. If you do not have an air filter could the engine have sucked up a rag and lodged it in the turbo? With the engine running excessively rich it will wash down the cylinder walls and force diesel into the crankcase.
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