Fuel from exhaust

The friendliest place on the web for anyone who enjoys boating.
If you have answers, please help by responding to the unanswered posts.
See posts with no answers
Y

yoeman

Veteran Member
Joined
Aug 21, 2013
Messages
49
Location
Canada
Vessel Name
Mojo
Vessel Make
Tollycraft 34 tricabin
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
 
is start up smoke new? Any sign of fuel in lube oil? start promptly from cold? Reach rated rpm under load?
 
Could it be gear oil from the cooler. Transfer cooler?
 
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.
 
Xsbank said:
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.
Click to expand...
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
 
yoeman said:
Nice to hear it may be normal......
I will wait and see how bad it really us before pulling injectors
Click to expand...

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.
 
yoeman said:
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
Click to expand...

My 99 5.9 6bta has a sheen until the engine warms up. My mechanic says its fine.
 
Congrats on having a 34' Tolly! Sedan' tri cabin, or sun deck model... what year? Those orig engines or replacements?? Go Tolly GO!!!!!!!!!!
 
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.
 
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.
 
C lectric said:
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.
Click to expand...

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.
 
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.
 
yoeman said:
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
Click to expand...

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;)
 
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.
 
for lots of slow running in cold water areas a higher temp thermostats (180) will keep engine temps up
 
Yes,
I should have mentioned to keep an eye on the gear oil levels. It is possible that they leak at the oil cooler.
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.
 
$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.
 
C lectric; said:
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.
Click to expand...
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!
 
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
 
I had this issue on our 330 Cummins (mechanical injectors) a few years ago. Turned out to be one failed injector. Next time you start, check the exhaust flange temperature of each cylinder as the engine warms up. Any cylinder lagging behind in temp rise ........ check it's injector. Watched the Cummins tech use this technique on our boat; now an optical pyrometer and spare injector are always on board.
 
The pre qsb 6bta really struggles to be environmentally friendly. It has these electric heaters that heat the air after it goes through the intercooler when the engine is cold. I have to idle out of my marina for a long time and the engine doesnt warm up until i can get the engine up to 1200 rpm or so. Meanwhile, during low rpm, these air heaters are going on and off and my voltage goes down to 9v when the heater is on, then pops back up to 14 when it is off. On for 5 secs or so, then off for 5 secs or so. We measured the temperature of the alternator during one of these runs through the harbor and it was like 3000 degrees. Needless to say, I disconnected the air heaters. A friend of mine with the same engine has his air heaters on a switch, but i dont know why. He says he never turns the heaters on. Anyhow, I think the air heaters were meant to cut down on the unburned fuel coming out of the exhaust.
 
Jetstream said:
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
Click to expand...

While this is technically possible, it is more likely that seawater finds its way into your fuel system than the other way around. Ask me how I know....:banged: :ermm:
 
bligh said:
The pre qsb 6bta really struggles to be environmentally friendly. It has these electric heaters that heat the air after it goes through the intercooler when the engine is cold. I have to idle out of my marina for a long time and the engine doesnt warm up until i can get the engine up to 1200 rpm or so. Meanwhile, during low rpm, these air heaters are going on and off and my voltage goes down to 9v when the heater is on, then pops back up to 14 when it is off. On for 5 secs or so, then off for 5 secs or so. We measured the temperature of the alternator during one of these runs through the harbor and it was like 3000 degrees. Needless to say, I disconnected the air heaters. A friend of mine with the same engine has his air heaters on a switch, but i dont know why. He says he never turns the heaters on. Anyhow, I think the air heaters were meant to cut down on the unburned fuel coming out of the exhaust.
Click to expand...

My heaters are still hooked up. With the engines off and using these heaters like a preheater, the voltage drop is about half of a volt...without the assistance of an alternator. So your batteries must have been near death if that is how it happened. I have never seen so much as a twitch with the engines running. But yes, the engines do take a while to heat up...and I don't think it has anything to do with these heaters....
 
The heater will suck a LOT of amps and will shorten the life of your alternator precipitously. It's not needed for marine use, they start fine without (my Cummins has no heaters) but you must warm up with a load. Start and leave the dock right away and no "winter warming" not in gear.
Baker, your description of how your heaters work is opposite to how my friends with Cummins heaters work. I think yours are malfunctioning and that's a good thing.
 
I kept the air heater on my 450 Cummins, but put a switch on the helm. It does help on winter starts where engine is like 40F. Not needed for starting there, but it does reduce the smoke til it is warmed up.

99% of the time the air heater is left off to avoid punishing the alternator.
 
Baker said:
My heaters are still hooked up. With the engines off and using these heaters like a preheater, the voltage drop is about half of a volt...without the assistance of an alternator. So your batteries must have been near death if that is how it happened. I have never seen so much as a twitch with the engines running. But yes, the engines do take a while to heat up...and I don't think it has anything to do with these heaters....
Click to expand...

The start battery is new and in good condition. My mechanic told me he disconnects most of these heaters in these engines since it puts such a huge load on the alternator. He also told says most of the preheaters that are this age have failed by now to begin with. Maybe you have a bigger alternator than i do or your preheaters aren't working. This is a known issue with the pre-2000 6bta and is well understood by most NT owners.
 
You must log in or register to reply here.

Similar threads

Jmreim
Fuel in Exhaust on cold start
Replies
12
Views
801
Jmreim
Jmreim
Shrew
Service/Maintenance
Replies
8
Views
735
O C Diver
O C Diver
J
Bluish smoke- oil or unburnt Fuel?
2
Replies
30
Views
3K
jefndeb
J
PhilPB
Fuel Filters
Replies
15
Views
2K
jleonard
jleonard
Sababa
Generator Smoke and Soot Under Load
2
Replies
54
Views
4K
Sykes
Sykes

Latest posts

Back
Top Bottom