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Old 04-10-2016, 03:34 PM   #1
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Fuel from exhaust

Cummings 5.9 6bta 250 hp 1999
Low hour engine that runs great
Symptoms are that when I cold start the engine I see a line of fuel in the water round the exhaust
I've never noticed this before and am guessing it's not a good thing
Any ideas on this
The engine has not had the injectors tested or any other items looked at
The boat has been sitting all winter and we only ran the engine for 15 minutes
It does smoke on start up
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Old 04-10-2016, 03:48 PM   #2
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is start up smoke new? Any sign of fuel in lube oil? start promptly from cold? Reach rated rpm under load?
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Old 04-10-2016, 04:56 PM   #3
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Could it be gear oil from the cooler. Transfer cooler?
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Old 04-10-2016, 05:14 PM   #4
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First of all, a small amount of fuel in the water is pretty common for these old mechanical injection engines. On its own, no worries. It evaporates. Presumably you are warming your engine in gear, with a nice load? All these engines will put out some smoke, they are pretty crude and their fuel mapping and efficiency is best at some cruising rpm with a load. The smoke is supposed to go away when the engine is at normal operating temperature.

All of this is if the engine runs well. And if you are keeping up with regular maintenance, fluid changes etc as per the Cummins manual?

If the engine is new to you, assume it has not been looked after and do one of the major maintenance routines like the one for 1000 hours to establish a baseline.
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Old 04-10-2016, 06:36 PM   #5
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Quote:
Originally Posted by Xsbank View Post
First of all, a small amount of fuel in the water is pretty common for these old mechanical injection engines. On its own, no worries. It evaporates. Presumably you are warming your engine in gear, with a nice load? All these engines will put out some smoke, they are pretty crude and their fuel mapping and efficiency is best at some cruising rpm with a load. The smoke is supposed to go away when the engine is at normal operating temperature.

All of this is if the engine runs well. And if you are keeping up with regular maintenance, fluid changes etc as per the Cummins manual?

If the engine is new to you, assume it has not been looked after and do one of the major maintenance routines like the one for 1000 hours to establish a baseline.
Nice to hear it may be normal
The smoke on start is not new and it does clear up after warm up
The engines are new to me and I'm doing some work on them to get a base line if service
New filters
Water pumps
Oil and filters
Coolers removed and cleaned
I have not adjusted the valves
Thanks for the reply so
I will wait and see how bad it really us before pulling injectors
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Old 04-10-2016, 09:18 PM   #6
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Nice to hear it may be normal......
I will wait and see how bad it really us before pulling injectors
It is not at all uncommon for this to happen. The engine is cold and the fuel mixture is not completely atomized so some of unburned fuel comes out in the exhaust. I would not worry about it. Smoking on start up si not a big deal either as long as it clears up.
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Old 04-10-2016, 09:20 PM   #7
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Originally Posted by yoeman View Post
Cummings 5.9 6bta 250 hp 1999
Low hour engine that runs great
Symptoms are that when I cold start the engine I see a line of fuel in the water round the exhaust
I've never noticed this before and am guessing it's not a good thing
Any ideas on this
The engine has not had the injectors tested or any other items looked at
The boat has been sitting all winter and we only ran the engine for 15 minutes
It does smoke on start up
My 99 5.9 6bta has a sheen until the engine warms up. My mechanic says its fine.
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Old 04-10-2016, 10:26 PM   #8
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Congrats on having a 34' Tolly! Sedan' tri cabin, or sun deck model... what year? Those orig engines or replacements?? Go Tolly GO!!!!!!!!!!
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Old 04-11-2016, 12:51 AM   #9
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I'll confuse the issue a bit.
When you crank the engine the injection pump goes to full fuel. It sees cranking as less than the asked for minimum setpoint of IDLE revs. So it cranks up full fuel to gain speed. As soon as the engine fires up and speeds up the governor sees the revs rise and cuts back the fuel to control rpm to idle.

Some /much of that unburned fuel has gone right through the engine into the exhaust system so it is normal to see it on the water as it gets blown out.

After start smoke. Once running the idle speed fuel is not burned cleanly. The combustion chamber is cold enough the fuel burns poorly so you get the smoke. Get the boat moving and under a light load ASAP. It will warm up and the smoke should disappear.

Get all ready to cast off except for the last lines needed. Then start , wait a moment for the engine to stabilize and then go at a light load for the engine to warm.

And as pointed out the mechanical engines are not as clean as the electronic engines, especially the common rail engines.
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Old 04-11-2016, 01:30 AM   #10
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Originally Posted by C lectric;
I'll confuse the issue a bit.
Not confusing at all. Pretty simple explanation that makes sense to me.
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Old 04-11-2016, 06:54 AM   #11
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A slight discoloration of the water could also be lube oil.

The rings need the cylinders to get warm to be back in shape , and a warm under load engine for everything to seal properly.

Once the coolant gets to 140F -160F the exhaust smoke should be gone and no staining from the discharge water.
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Old 04-11-2016, 08:41 AM   #12
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I'll confuse the issue a bit.
When you crank the engine the injection pump goes to full fuel. It sees cranking as less than the asked for minimum setpoint of IDLE revs. So it cranks up full fuel to gain speed. As soon as the engine fires up and speeds up the governor sees the revs rise and cuts back the fuel to control rpm to idle.

Some /much of that unburned fuel has gone right through the engine into the exhaust system so it is normal to see it on the water as it gets blown out.

After start smoke. Once running the idle speed fuel is not burned cleanly. The combustion chamber is cold enough the fuel burns poorly so you get the smoke. Get the boat moving and under a light load ASAP. It will warm up and the smoke should disappear.

Get all ready to cast off except for the last lines needed. Then start , wait a moment for the engine to stabilize and then go at a light load for the engine to warm.

And as pointed out the mechanical engines are not as clean as the electronic engines, especially the common rail engines.
This is the correct way to start and warm diesels. They don't warm much unless slightly loaded but may smoke, dribble fuel and carbon up inside. Start them and go is best for many reasons. Just don't go above a medium slow speed until temp is up.
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Old 04-11-2016, 10:06 AM   #13
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Yoeman

If not done already, visit boatdiesel.com. It is a great Cummins site and I'd guess you would quickly be dispelled from messing with your injectors. The other work items you mention are good to do.

BTW, great boat and engine combination. It should prove a very economical 20 knot cruiser. Lots of Tolly lovers and experiences in the WA and BC area.

I'm in complete agreement with C electric who by the way is one of the smart BC posters on boatdiesel so you are getting two bangs for the loonie.
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Old 04-11-2016, 11:16 AM   #14
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Quote:
Originally Posted by yoeman View Post
Cummings 5.9 6bta 250 hp 1999
Low hour engine that runs great
Symptoms are that when I cold start the engine I see a line of fuel in the water round the exhaust
I've never noticed this before and am guessing it's not a good thing
Any ideas on this
The engine has not had the injectors tested or any other items looked at
The boat has been sitting all winter and we only ran the engine for 15 minutes
It does smoke on start up
We have a 1989 6BT5.9M 210 HP. It does the same thing. Smokes a little on start up and has a small sheen at the exhaust. Once at temp it all goes away. While cruising the locks in Canada the smoke and sheen would return if we idled for very long periods waiting for and between locks. Probably due to the engine cooling off due to no load. 2cents
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Old 04-11-2016, 11:57 AM   #15
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Keep a close eye on gear oil level and color, the sheen could be a leak in the gear cooler.

Otherwise, a little smoke and fuel sheen is normal on a cold mechanical B-motor.
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Old 04-11-2016, 02:24 PM   #16
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for lots of slow running in cold water areas a higher temp thermostats (180) will keep engine temps up
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Old 04-11-2016, 11:36 PM   #17
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Yes,
I should have mentioned to keep an eye on the gear[s] oil levels. It is possible that they leak at the oil cooler[s].
If the coolers you have now DO NOT have zincs, and some of the Cummins ones don't [Champ], then watch them carefully as they have been found to have a relatively short life compared to the better ones [Sendure].

Yes, look up Boatdiesel and also Seaboard Marine [TOny Athens] site who is a strong supporter of B.D. and has given a huge amount of info for free which we can all make use of if the time is spent to read and understand.
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Old 04-12-2016, 12:01 AM   #18
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$250,000 Reward for Reporting Pollution | Oceana USA

So can you get paid for turning in your fellow boaters who put a 'sheen' on the water?

I never have, but one time at the fuel dock, some small gas got spilled by someone filling up and this retired snooty rich guy comes by smells the gas and starts getting angry.
The fuel attendant calmly cleans up a little and you know it was a very windy day, all the little ripples on the water, you could not see anything on the water at all.

But the older snooty rich busy body was hopping mad at the owner of the boat fueling up. Threatened to call the USCG. I suppose if it had been diesel, the tiny spill might have been more visible.
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Old 04-12-2016, 01:31 AM   #19
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Originally Posted by C lectric;
Yes, look up Boatdiesel and also Seaboard Marine [Tony Athens] site who is a strong supporter of B.D. and has given a huge amount of info for free which we can all make use of if the time is spent to read and understand.
Totally agree. The Seaboard Marine site is an amazing resource. I doubt I will ever make it through all the "Tony's Tips."

The man has to love what he does to give so much...thank you Tony!
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Old 04-12-2016, 06:15 AM   #20
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I'd agree with all the comments so far that it is pretty normal for the 6bta to have a slight fuel sheen out the exhaust on start up but it also might be worth having a look at you fuel coolers. When they get older they can leek into the cooling raw water. The fix is either replace them to get rid of them with a kit from Seaboard Marine,

Brett
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