Loose Injector

[Tom_Barb]

Has any one heard of the Cummins 8.3 ISC having a loose injector causing combustion products to enter the return fuel going back to the main tank and causing the fuel to turn black, then clogging filters when delivered to the engine, on the supply line?

Don't tell me Algae, we know it isn't.

This debris is a fine carbon particles as is found in engine oil and the combustion chamber. (soot) 99% will pass a 10 micron filter, but that 1% will clog a filter every 10k miles.

Things done so far:
tank removed and cleaned, (thinking we got a load of bad fuel.) 10k miles later fuel is black again, and filters clogged.
New filters installed, 12k miles later they are clogged again. fuel is black.
All hoses removed and replaced. tank cleaned again. (10k miles later fuel is black again, and filters clogged)

Engine runs strong, until we get a low fuel pressure light and a code of low fuel pressure. change both the engine and chassis filters ad it will run strong again for 10k+ miles.
This engine will not use 1 qt of oil between 15k mile oil & filter changes.

I'd like to know of any other 8.3 ISC engines that have had a loose injector? this engine has done this since day one mile one. 43k miles later we are still trying to figure out why it will return black fuel to the main tank.

[down_home]

donfrump wrote:

down home wrote:
What about the seals between sections in the turbo?

fuel does not go thru or near the turbo OP has black fuel

OP? I find it incredible that cummins is unable to diagnose or repair this issue

My bad, wrong gear.

[Tom_Barb]

11178adm wrote:
on ISC8.3 CAPS pumps the injector has as previously mentioned has a crush washer to seal the injector from the combustion chamber the high pres fuel line feeds the injector through a quill tube that is held into the side of the injector with a nut in the side of the head, there is a oring near the top of the injector to seal any fuel that leaks between the quill tube and injector from leaking into the oil, there is a passage in the head that connects to a return line at the rear of the head. if one of the crush washers is leaking combustion gas would get into the return fuel and go back to the fuel tank. you might be able to verify this with a temporary clear plastic line installed in the fuel return and looking for air in the fuel but this type of leak usually will only show up on a hard pull. if the engine performs well probably all that would be needed would be the seals and orings. the compression seals are copper seals about 3/8 in long that sometimes stick in the head and can be difficult to remove. the leaking inj seal should have carbon accumulation above the compression seal area make sure to clean and examine the inj bore and the inj for erosion

this is the present thinking of Cummins tech. We are due for our 48 mile valve adjustment, so we are going to have the injectors removed and re-sealed. we will see what they say after the work.

[11178adm]

on ISC8.3 CAPS pumps the injector has as previously mentioned has a crush washer to seal the injector from the combustion chamber the high pres fuel line feeds the injector through a quill tube that is held into the side of the injector with a nut in the side of the head, there is a oring near the top of the injector to seal any fuel that leaks between the quill tube and injector from leaking into the oil, there is a passage in the head that connects to a return line at the rear of the head. if one of the crush washers is leaking combustion gas would get into the return fuel and go back to the fuel tank. you might be able to verify this with a temporary clear plastic line installed in the fuel return and looking for air in the fuel but this type of leak usually will only show up on a hard pull. if the engine performs well probably all that would be needed would be the seals and orings. the compression seals are copper seals about 3/8 in long that sometimes stick in the head and can be difficult to remove. the leaking inj seal should have carbon accumulation above the compression seal area make sure to clean and examine the inj bore and the inj for erosion

[Tom_Barb]

donfrump wrote:

OP? I find it incredible that cummins is unable to diagnose or repair this issue

Me too. They have been very good at sending illustrated parts break downs and numbers. and ideas. check here, do this, type stuff.

[donfrump]

down home wrote:
What about the seals between sections in the turbo?

fuel does not go thru or near the turbo OP has black fuel

OP? I find it incredible that cummins is unable to diagnose or repair this issue

[Tom_Barb]

down home wrote:
What about the seals between sections in the turbo?

Wouldn't it smoke like a smudge pot ? and use oil like crazy?

[down_home]

What about the seals between sections in the turbo?

[Tom_Barb]

donfrump wrote:
U indicate u know the fix so then fix it

One must remember the original question. Have you ever heard of a loose injector causing black fuel?

We have thought we had this cured before, But ?

[Tom_Barb]

donfrump wrote:

Tom/Barb wrote:

Old-Biscuit wrote:
15 yrs :H

It was already 9 years old when we bought it. and it takes time to trouble shoot, fix, then put 10k miles on it to discover that it is still doing it.

If it was that old when u bought how(as claimed) do u no it has done this since new?
U indicate u know the fix so then fix it

I think I would install a fuel return filter system that's easy to get at and buy some cheap fuel filters and live with it
Like u say it runs perfect and uses no oil,good power etc

Understand, it had 8600 miles on it when we bought it, at 12,000 miles we had our first filter clogging issue. and thats has been the interval ever since.
It was in dry storage for over 9 years 2000-2009 due to health issues of the previous owner.

[donfrump]

Tom/Barb wrote:

Old-Biscuit wrote:
15 yrs :H

It was already 9 years old when we bought it. and it takes time to trouble shoot, fix, then put 10k miles on it to discover that it is still doing it.

If it was that old when u bought how(as claimed) do u no it has done this since new?
U indicate u know the fix so then fix it

I think I would install a fuel return filter system that's easy to get at and buy some cheap fuel filters and live with it
Like u say it runs perfect and uses no oil,good power etc

[Tom_Barb]

sjholt wrote:
After looking at this thread a second time, I see that "under the microscope there is a hard particle"?
That would mean to me that there is hot exhaust getting into the fuel system under high pressure. I would suspect a cracked head. Somehow the fuel is getting burned to create a hard particle.
Maybe a compression check would verify it? Maybe not. Is there a fuel passage way in the head?

If the filter changes/mileage remains the same, then I would just change them every so often and keep on driving.
JMHO

Changing fuel filters at 10k miles is what we have been doing as a precaution because we know they will be clogged by 12-13K.

Most of our maintenance was completed in the 2011-2013 / 20,000 -25,000 mile time frame, but the problem still exist at 43,000. this is always on our minds when we take it on the road.

The cracked head theory is a possibility but it is not supported by any other typical head cracked symptoms. no coolant disappearing, no coolant in the oil. type stuff.

[Tom_Barb]

Old-Biscuit wrote:
15 yrs :H

It was already 9 years old when we bought it. and it takes time to trouble shoot, fix, then put 10k miles on it to discover that it is still doing it.

[sjholt]

After looking at this thread a second time, I see that "under the microscope there is a hard particle"?
That would mean to me that there is hot exhaust getting into the fuel system under high pressure. I would suspect a cracked head. Somehow the fuel is getting burned to create a hard particle.
Maybe a compression check would verify it? Maybe not. Is there a fuel passage way in the head?

If the filter changes/mileage remains the same, then I would just change them every so often and keep on driving.
JMHO

[Old-Biscuit]

15 yrs :H