Excess fuel to the pumps goes to the return line. Unburnt fuel is fuel that
was injected and did not burn. Bad injector that does not atomize the fuel
well, or injects too much fuel allows the fuel to not get burnt, and comes
out the exhaust. Diesel semi's that are blowing black smoke are ejecting
unburnt fuel.
Bill

"Dave R" wrote in message
...
I don't think I can give you any advice but I just have a question. I've
driven trucks all my life and by your post you say the problem might be
unburnt fuel. That's what puzzles me. Every diesel I've driven always have
a
return line to the tank for unburnt fuel. Please forgive me if I
completely
ignorant on marine diesels but why would they not have a return line? I
can
tell you that the little amount of either that you used would not hurt
anything. What kind of outside temps has your fuel been in? And how long
has
the diesel been in the tank? Have you switched fuel. Did you burn #1 or #2
diesel. Is it low sulfur diesel? I ask these questions because 4K hours to
me is not a whole lot of hours.
"Mike" wrote in message
om...
I have 2 Cummins 6bt5.7M (4k hours) that are beginning to smoke and
leave a film at the exhaust (sea water output). The port engine is the
worst, but both engines have the same problem. In trying to identify
the problem I've preformed the following test.
1) no (or very little) oil usage.
2) Both Engines run at 180 deg.
3) Turbo output 2600rpm (port)16psi (starb) 18psi Cummins manual
calls for 20-25psi. No intake obstructions. No leaks detected any
place from output of turbo up to and including the intake manifold. No
detectable leaks in exhaust. No restrictions in oil return line.
4) Turbo (Holset H1C) compressor impeller can be pushed to contact the
housing. (I would guess .100" movement) Holset calls for .012" -
.018" radial movement
5) Turbo axial movement .010 both sides. Holset calls for .025.
6) Blowby (taken with the Cummins recommend setup using calibrated
0-100"h20 gauge with dipstick hole blocked). at 1000rpm approx. 2"
(both engines) but at 2600 rpm 0".
(I've ordered a diesel compression tester hope to have it next weekend
while I'm testing the compression, I'll get the injectors tested)

These are the steps that I've taken so far. The most glaring result to
me is the blowby. There is none detected at rated speed. I've talked
to the Cummins dealer, he says that it can't be and recommend using a
manometer instead of the gauge.
The turbo's are bad according to the holset manual so I pulled them
and brought them to be rebuilt (holset authorized). The mechanic
looked at them when I dropped them off and While he didn't come out
and say so, I got the impression that he thought they were ok. He will
be taking them apart this week.

OK, now for my diagnosis;
The smoke and sheen that I see are unburned diesel. The cause is low
turbo pressure not getting enough air into the cylinders. The low
turbo pressure is
Caused by bad oil seals in the turbos allowing crankcase pressure to
be reduced by the vacuum of the turbo compressor. The question of why
would both engines have the same problem comes up. My theory is; when
changing fuel filters, I use starting fluid to get the fuel to start.
The ether (or other chemicals in the starting fluid) has caused the
seal to deteriorate.

Anyone have any feedback? The engines are honey's. They have never
failed in the 10 years we've owned the boat ( 3000hrs). The smoke is
not a killer yet, but I would like to solve the problem before it gets
worse.

Thanking anyone in advance for advice, criticism or observations.

Mike

"Mike" wrote in message

I have 2 Cummins 6bt5.7M (4k hours) that are beginning to smoke and
leave a film at the exhaust (sea water output).

Is this at all speeds, or only under wide open throttle? (okay, diesels
aren't throttled, but I never picked up what the proper term for a diesel
is....). If it is WOT only, is this slick so obvious you can see it going
full speed?

Other than the oil in the water, how are the engines running? Still giving
you the same performace as before? How about fuel usage?


3) Turbo output 2600rpm (port)16psi (starb) 18psi Cummins manual
calls for 20-25psi.

Is this measurement taken while under load, or while in neutral? I
wouldn't expect the turbos to be working very hard unless the engines were
heavily loaded. Engine RPM does not indicate turbo RPM.

OK, now for my diagnosis;
The smoke and sheen that I see are unburned diesel.

Probably.

The cause is low turbo pressure not getting enough air into the
cylinders.

Only if this problem is occuring at or near WOT conditions. If this problem
happens at idle speeds (which is when I would expect you would be able to
see the sheen in your wake) then it isn't the turbo.

The low turbo pressure is
Caused by bad oil seals in the turbos allowing crankcase pressure to
be reduced by the vacuum of the turbo compressor.

I don't follow you here.

If there aren't any obstructions in the turbo intake (like an air filter)
then there shouldn't be much vacuum generated. I am not familiar with this
engine at all, so I don't understand how the crankcase pressure and turbo
are related (the turbos I am familiar with have been mounted external to the
engine and don't have any connection to the crankcase that could leak).

If the problem were bad oil seals, however, then I would expect that there
would be a loss of oil. If the leak went external then it should be making
a mess in the engine room. If the leak went internal then I would expect it
to just be burned, only showing up in the fact that you have to add oil
often.



Anyone have any feedback? The engines are honey's. They have never
failed in the 10 years we've owned the boat ( 3000hrs). The smoke is
not a killer yet, but I would like to solve the problem before it gets
worse.


When was the last time you had the injectors serviced?

A diesel engine requires a little bit more than just squirting the fuel into
the cylinder. Part of the injectors job is to atomize the fuel as it is
injected so that it can burn. Vaporized fuel will ignite and burn. Liquid
fuel will NOT burn.

A worn injector can allow a portion of the fuel to enter as a liquid stream.
Some of this will boil and burn, but portions of it will remain liquid, not
burn and then go out the exhaust, causing your problem.

The last time I had injectors serviced it cost me $125 an injector. I took
them off, brought them down to a shop that specializes in diesel fuel
systems. They had them about a day and then I picked them up and put them
back on. An engine I was about ready to throw the towel in on ran great
after that.

If your injectors have 3000 hours on them, then I wouldn't hesitate to have
them serviced.


Rod

"Rod McInnis" wrote in message ...
"Mike" wrote in message

I have 2 Cummins 6bt5.7M (4k hours) that are beginning to smoke and
leave a film at the exhaust (sea water output).

- Is this at all speeds, or only under wide open throttle? (okay, diesels
-aren't throttled, but I never picked up what the proper term for a diesel
-is....). If it is WOT only, is this slick so obvious you can see it going
-full speed?

-Other than the oil in the water, how are the engines running? Still giving
-you the same performace as before? How about fuel usage?

They are both smoking at all speeds, port more than starbord. Other than the
smoke (again, not exceesive but more that I would like)



3) Turbo output 2600rpm (port)16psi (starb) 18psi Cummins manual
calls for 20-25psi.

- Is this measurement taken while under load, or while in neutral? I
-wouldn't expect the turbos to be working very hard unless the engines were
-heavily loaded. Engine RPM does not indicate turbo RPM.

This is taken full throttle (I don't know what else to call it either)
under load (about 16knts).

OK, now for my diagnosis;
The smoke and sheen that I see are unburned diesel.

- Probably.



The cause is low turbo pressure not getting enough air into the
cylinders.

-Only if this problem is occuring at or near WOT conditions. If this problem
-happens at idle speeds (which is when I would expect you would be able to
-see the sheen in your wake) then it isn't the turbo.

there seems to be more smoke at idle speeds. That may be because the
there is air movement.

I talked to the turbo rebuild tech today, he found one bad turbo, (exhaust
blade hitting the housing) the port side. He said the starboard was in
fair condition.

The low turbo pressure is
Caused by bad oil seals in the turbos allowing crankcase pressure to
be reduced by the vacuum of the turbo compressor.

-I don't follow you here.

-If there aren't any obstructions in the turbo intake (like an air filter)
-then there shouldn't be much vacuum generated. I am not familiar with this
-engine at all, so I don't understand how the crankcase pressure and turbo
-are related (the turbos I am familiar with have been mounted external to the
-engine and don't have any connection to the crankcase that could leak).

-If the problem were bad oil seals, however, then I would expect that there
-would be a loss of oil. If the leak went external then it should be making
-a mess in the engine room. If the leak went internal then I would expect it
-to just be burned, only showing up in the fact that you have to add oil
-often.

Yeah, I don't blame you for being confused, I worked out this elaborate
scenerio to explain the lack of blowby.



Anyone have any feedback? The engines are honey's. They have never
failed in the 10 years we've owned the boat ( 3000hrs). The smoke is
not a killer yet, but I would like to solve the problem before it gets
worse.


-When was the last time you had the injectors serviced?

-A diesel engine requires a little bit more than just squirting the fuel into
-the cylinder. Part of the injectors job is to atomize the fuel as it is
-injected so that it can burn. Vaporized fuel will ignite and burn. Liquid
-fuel will NOT burn.

-A worn injector can allow a portion of the fuel to enter as a liquid stream.
-Some of this will boil and burn, but portions of it will remain liquid, not
-burn and then go out the exhaust, causing your problem.

-The last time I had injectors serviced it cost me $125 an injector. I took
-them off, brought them down to a shop that specializes in diesel fuel
-systems. They had them about a day and then I picked them up and put them
-back on. An engine I was about ready to throw the towel in on ran great
-after that.

-If your injectors have 3000 hours on them, then I wouldn't hesitate to have
-them serviced.

Whoa! 125/injector...
I agree, I will be removing them as soon as I get the turbos back on. (hopefully
this weekend).


Thanks a lot for the response Rod.

If the engines are turbo intercooled it might be that the intercooler is
partially blocked
the induction air is too hot and has of low density
giving incomplete combustion
Good Luck!!
Steve


"Mike" wrote in message
om...
I have 2 Cummins 6bt5.7M (4k hours) that are beginning to smoke and
leave a film at the exhaust (sea water output). The port engine is the
worst, but both engines have the same problem. In trying to identify
the problem I've preformed the following test.
1) no (or very little) oil usage.
2) Both Engines run at 180 deg.
3) Turbo output 2600rpm (port)16psi (starb) 18psi Cummins manual
calls for 20-25psi. No intake obstructions. No leaks detected any
place from output of turbo up to and including the intake manifold. No
detectable leaks in exhaust. No restrictions in oil return line.
4) Turbo (Holset H1C) compressor impeller can be pushed to contact the
housing. (I would guess .100" movement) Holset calls for .012" -
.018" radial movement
5) Turbo axial movement .010 both sides. Holset calls for .025.
6) Blowby (taken with the Cummins recommend setup using calibrated
0-100"h20 gauge with dipstick hole blocked). at 1000rpm approx. 2"
(both engines) but at 2600 rpm 0".
(I've ordered a diesel compression tester hope to have it next weekend
while I'm testing the compression, I'll get the injectors tested)

These are the steps that I've taken so far. The most glaring result to
me is the blowby. There is none detected at rated speed. I've talked
to the Cummins dealer, he says that it can't be and recommend using a
manometer instead of the gauge.
The turbo's are bad according to the holset manual so I pulled them
and brought them to be rebuilt (holset authorized). The mechanic
looked at them when I dropped them off and While he didn't come out
and say so, I got the impression that he thought they were ok. He will
be taking them apart this week.

OK, now for my diagnosis;
The smoke and sheen that I see are unburned diesel. The cause is low
turbo pressure not getting enough air into the cylinders. The low
turbo pressure is
Caused by bad oil seals in the turbos allowing crankcase pressure to
be reduced by the vacuum of the turbo compressor. The question of why
would both engines have the same problem comes up. My theory is; when
changing fuel filters, I use starting fluid to get the fuel to start.
The ether (or other chemicals in the starting fluid) has caused the
seal to deteriorate.

Anyone have any feedback? The engines are honey's. They have never
failed in the 10 years we've owned the boat ( 3000hrs). The smoke is
not a killer yet, but I would like to solve the problem before it gets
worse.

Thanking anyone in advance for advice, criticism or observations.

Mike

The Cummins system senses manifold pressure so although your turbos
need service (maybe) the lower pressure shouldn't mean excess fuel
getting injected.

Certainly get the unit injectors serviced, it's more likely poor fuel
injection pressure or atomisation causing the unburnt fuel out the exhaust.

Once the injectors are up to snuff, the new performance will probably
bring the turbo pressure up a bit also.

The turbo(s) have full floating plain bearings with lots of
clearance/play in all directions so despite being more than "spec" if
they're not allowing oil "in" they are not likely to be the root cause
of your problem.


K


Mike wrote:
I have 2 Cummins 6bt5.7M (4k hours) that are beginning to smoke and
leave a film at the exhaust (sea water output). The port engine is the
worst, but both engines have the same problem. In trying to identify
the problem I've preformed the following test.
1) no (or very little) oil usage.
2) Both Engines run at 180 deg.
3) Turbo output 2600rpm (port)16psi (starb) 18psi Cummins manual
calls for 20-25psi. No intake obstructions. No leaks detected any
place from output of turbo up to and including the intake manifold. No
detectable leaks in exhaust. No restrictions in oil return line.
4) Turbo (Holset H1C) compressor impeller can be pushed to contact the
housing. (I would guess .100" movement) Holset calls for .012" -
.018" radial movement
5) Turbo axial movement .010 both sides. Holset calls for .025.
6) Blowby (taken with the Cummins recommend setup using calibrated
0-100"h20 gauge with dipstick hole blocked). at 1000rpm approx. 2"
(both engines) but at 2600 rpm 0".
(I've ordered a diesel compression tester hope to have it next weekend
while I'm testing the compression, I'll get the injectors tested)

These are the steps that I've taken so far. The most glaring result to
me is the blowby. There is none detected at rated speed. I've talked
to the Cummins dealer, he says that it can't be and recommend using a
manometer instead of the gauge.
The turbo's are bad according to the holset manual so I pulled them
and brought them to be rebuilt (holset authorized). The mechanic
looked at them when I dropped them off and While he didn't come out
and say so, I got the impression that he thought they were ok. He will
be taking them apart this week.

OK, now for my diagnosis;
The smoke and sheen that I see are unburned diesel. The cause is low
turbo pressure not getting enough air into the cylinders. The low
turbo pressure is
Caused by bad oil seals in the turbos allowing crankcase pressure to
be reduced by the vacuum of the turbo compressor. The question of why
would both engines have the same problem comes up. My theory is; when
changing fuel filters, I use starting fluid to get the fuel to start.
The ether (or other chemicals in the starting fluid) has caused the
seal to deteriorate.

Anyone have any feedback? The engines are honey's. They have never
failed in the 10 years we've owned the boat ( 3000hrs). The smoke is
not a killer yet, but I would like to solve the problem before it gets
worse.

Thanking anyone in advance for advice, criticism or observations.

Mike

"K. Smith" wrote in message ...
The Cummins system senses manifold pressure so although your turbos
need service (maybe) the lower pressure shouldn't mean excess fuel
getting injected.

Certainly get the unit injectors serviced, it's more likely poor fuel
injection pressure or atomisation causing the unburnt fuel out the exhaust.

Once the injectors are up to snuff, the new performance will probably
bring the turbo pressure up a bit also.

The turbo(s) have full floating plain bearings with lots of
clearance/play in all directions so despite being more than "spec" if
they're not allowing oil "in" they are not likely to be the root cause
of your problem.


K



thanks for the reply K.
On of the turbo's did have serious a problem, but the other didn't.
The injectors are next on the list.

Mike wrote:

1) no (or very little) oil usage.
Check for fuel dilution.

3) Turbo output 2600rpm (port)16psi (starb) 18psi Cummins manual
calls for 20-25psi.
Worn turbos are less efficient. Worn bearings will limit turbine speed
and reduce output pressure. How much power or boat performance have you
lost? Turbo output pressure is related to the load on the engine, and
atmospheric pressure and temperature, not just rpm. There are a number
of reasons why the pressure might be low ... what was it before you
decided you had problems? Do you know what it was?

The smoke and sheen that I see are unburned diesel.
Are you positive it is fuel? Do the engines smoke black on acceleration
and under heavy loads? What color is the smoke at low speeds? How much
power have you lost?

turbo pressure not getting enough air into the cylinders. The low
turbo pressure is Caused by bad oil seals in the turbos allowing crankcase pressure to
be reduced by the vacuum of the turbo compressor.

????? Crankcase pressure related to turbo vacuum? Sorry but you have a
diesel, there is no "vacuum" created anywhere. There is a low pressure
area in front of the compressor wheel but unless your air inlet is
blocked there is no vacuum like you might see in a gasoline engine.

The only effect you would see if you have bad oil seals in the turbo
would be oil leaking into the charge air and being delivered to the
cylinders or blue oil smoke in the exhaust. Check the condition of the
intake piping to see if it is wet with oil, check the condition of the
exhaust from the turbo after a period of idling to see if it is wet with
oil. It sounds like that is irrelevant now that you have removed the
turbos for rebuild but file that away for the future.

Worn injectors will cause poor combustion and can create most of the
symptoms you describe.

As long as you have no starting problems you have no compression
problems. You may have cylinder wear and worn injectors which lead to
fuel dilution of the lube oil. This is cause for concern. Check with
Cummimns for their recommendation on maximum allowable dilution limits.

Good luck and get back to us with the results of your investigations.

Rick wrote in message ink.net...
Mike wrote:

1) no (or very little) oil usage.
Check for fuel dilution.
Thanks for the suggestion.I will add oil testing to the list.


3) Turbo output 2600rpm (port)16psi (starb) 18psi Cummins manual
calls for 20-25psi.
Worn turbos are less efficient. Worn bearings will limit turbine speed
and reduce output pressure. How much power or boat performance have you
lost? Turbo output pressure is related to the load on the engine, and
atmospheric pressure and temperature, not just rpm. There are a number
of reasons why the pressure might be low ... what was it before you
decided you had problems? Do you know what it was?

I first noticed the sheen this past November. The smoke has been increasing
over the last year or so. As for power, I can't say that I've notice any
change. Most of my cruising is done around 1800 rpm (8-9knts)

The smoke and sheen that I see are unburned diesel.
Are you positive it is fuel? Do the engines smoke black on acceleration
and under heavy loads? What color is the smoke at low speeds? How much
power have you lost?

If I throttle up rapidly while underway, the smoke is black until the boat
gets up on a plane, then to white (slight blue mabey). In all other conditions
the smoke is whitish (slight blue mabey)

turbo pressure not getting enough air into the cylinders. The low
turbo pressure is Caused by bad oil seals in the turbos allowing crankcase pressure to
be reduced by the vacuum of the turbo compressor.

????? Crankcase pressure related to turbo vacuum? Sorry but you have a
diesel, there is no "vacuum" created anywhere. There is a low pressure
area in front of the compressor wheel but unless your air inlet is
blocked there is no vacuum like you might see in a gasoline engine.

with the air filters on there is a slight vacuum that increases as the air
filter gets dirty.

The only effect you would see if you have bad oil seals in the turbo
would be oil leaking into the charge air and being delivered to the
cylinders or blue oil smoke in the exhaust. Check the condition of the
intake piping to see if it is wet with oil, check the condition of the
exhaust from the turbo after a period of idling to see if it is wet with
oil. It sounds like that is irrelevant now that you have removed the
turbos for rebuild but file that away for the future.

Worn injectors will cause poor combustion and can create most of the
symptoms you describe.

As long as you have no starting problems you have no compression
problems. You may have cylinder wear and worn injectors which lead to
fuel dilution of the lube oil. This is cause for concern. Check with
Cummimns for their recommendation on maximum allowable dilution limits.

Good luck and get back to us with the results of your investigations.

The next step will be to get the injectors looked at. Then the oil test.
While I'm removing the injectors I will also get the compression. UPS
just delivered my diesel compression tester.


Thanks for the reply.

Mike

(Mike) wrote in message . com...
I have 2 Cummins 6bt5.7M (4k hours) that are beginning to smoke and
leave a film at the exhaust (sea water output). The port engine is the
worst, but both engines have the same problem. In trying to identify
the problem I've preformed the following test.
1) no (or very little) oil usage.
2) Both Engines run at 180 deg.
3) Turbo output 2600rpm (port)16psi (starb) 18psi Cummins manual
calls for 20-25psi. No intake obstructions. No leaks detected any
place from output of turbo up to and including the intake manifold. No
detectable leaks in exhaust. No restrictions in oil return line.
4) Turbo (Holset H1C) compressor impeller can be pushed to contact the
housing. (I would guess .100" movement) Holset calls for .012" -
.018" radial movement
5) Turbo axial movement .010 both sides. Holset calls for .025.
6) Blowby (taken with the Cummins recommend setup using calibrated
0-100"h20 gauge with dipstick hole blocked). at 1000rpm approx. 2"
(both engines) but at 2600 rpm 0".
(I've ordered a diesel compression tester hope to have it next weekend
while I'm testing the compression, I'll get the injectors tested)

These are the steps that I've taken so far. The most glaring result to
me is the blowby. There is none detected at rated speed. I've talked
to the Cummins dealer, he says that it can't be and recommend using a
manometer instead of the gauge.
The turbo's are bad according to the holset manual so I pulled them
and brought them to be rebuilt (holset authorized). The mechanic
looked at them when I dropped them off and While he didn't come out
and say so, I got the impression that he thought they were ok. He will
be taking them apart this week.

OK, now for my diagnosis;
The smoke and sheen that I see are unburned diesel. The cause is low
turbo pressure not getting enough air into the cylinders. The low
turbo pressure is
Caused by bad oil seals in the turbos allowing crankcase pressure to
be reduced by the vacuum of the turbo compressor. The question of why
would both engines have the same problem comes up. My theory is; when
changing fuel filters, I use starting fluid to get the fuel to start.
The ether (or other chemicals in the starting fluid) has caused the
seal to deteriorate.

Anyone have any feedback? The engines are honey's. They have never
failed in the 10 years we've owned the boat ( 3000hrs). The smoke is
not a killer yet, but I would like to solve the problem before it gets
worse.

Thanking anyone in advance for advice, criticism or observations.

Mike

Mike,

Between having the turbo's redone, they sound like they need to be,
and what their probably going to find with the injectors, poor pattern
or leaking, you should have this beaten, as long as the compression is
good. As far as why at the same time, first off, at 4000 hours, it
just might be time, and second, does the boat have an automatic
synchronizer, boats with them, if the master engine starts to go
before the slave, it's easy to miss this.

John

(John) wrote in message m...
(Mike) wrote in message
Mike,

Between having the turbo's redone, they sound like they need to be,
and what their probably going to find with the injectors, poor pattern
or leaking, you should have this beaten, as long as the compression is
good. As far as why at the same time, first off, at 4000 hours, it
just might be time, and second, does the boat have an automatic
synchronizer, boats with them, if the master engine starts to go
before the slave, it's easy to miss this.

John

I will be getting the injectors service as soon as the turbos are back on.
I will be checking the compression also. I do have sync so mabey...
Thanks John.