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

On 7 Mar 2004 17:11:04 -0800, (Mike) wrote:

~~ snippage ~~

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

Agreed.

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

It certainly could be that, but that's not the only answer. It could
also be too much fuel entering the chamber.

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.

Well, I can certainly buy that as a reason, but it's sort of unlikely
unless you use a whole can of it.

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.

I might want to have the fuel pumps checked at long as you are working
on the engines.

Later,

Tom
S. Woodstock, CT
-----------
"Do fishermen eat avocados? This is a question
that no one ever thinks to ask."

Russel Chatham, "Dark Waters" (1988)

Subject: Diesel troubleshooting
From: (Mike)

Try this site.

http://boatdiesel.com/Forums/Forums.cfm

Capt. Bill

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.

The low turbo pressure & excessive radial movement is definitely a
problem. New bearings? Good idea to get the injectors checked out too,
though.

FWIW I have a problem with a small diesel genset. I have rebuilt the
fuel supply system, and the engine ran fine unloaded, but after a while
started to bog down and then died. Sounds like a fuel restriction?
Anyway I did not have time to troubleshoot it this past weekend, maybe next.

Fair Skies
Doug King

On Mon, 08 Mar 2004 11:33:36 -0500, DSK wrote:

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.

The low turbo pressure & excessive radial movement is definitely a
problem. New bearings? Good idea to get the injectors checked out too,
though.

FWIW I have a problem with a small diesel genset. I have rebuilt the
fuel supply system, and the engine ran fine unloaded, but after a while
started to bog down and then died. Sounds like a fuel restriction?
Anyway I did not have time to troubleshoot it this past weekend, maybe next.

Is your generator a Kubota three cylinder? I had this exact same
problem last year with the one here at the house and it was crap in
the fuel tank and line - sludge actually.

Later,

Tom
S. Woodstock, CT
-----------
"Do fishermen eat avocados? This is a question
that no one ever thinks to ask."

Russel Chatham, "Dark Waters" (1988)

Short Wave Sportfishing wrote:
Is your generator a Kubota three cylinder? I had this exact same
problem last year with the one here at the house and it was crap in
the fuel tank and line - sludge actually.

I think it's a Yanmar, it's a Onan 4.5kW genset. It's a job for this
coming weekend, check the fuel flow. The filters are clear but it's
possible that the suction line connection to the tank is blocked.

Fair Skies
Doug King

If you really wish to get inteligent answers, you may want to try
rec.boats.cruising. It's a moderated group with boaters. No O.T. posts.

Subject: Diesel troubleshooting
From: (Florida Keyz)

If you really wish to get inteligent answers, you may want to try
rec.boats.cruising. It's a moderated group with boaters. No O.T. posts.


Is this OT post going to be your standard response to all questions on
rec.boats now?

And by the way, rec.boats.cruising it NOT moderated.

Capt. Bill

Florida Keyz,
I think you're wrong about this. The group is not moderated. True though
about the number of OT posts.
Paul

"Florida Keyz" wrote in message
...
If you really wish to get inteligent answers, you may want to try
rec.boats.cruising. It's a moderated group with boaters. No O.T. posts.

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