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.

Tom/Barb wrote: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.No a loose injector would never cause this situation however I have to ask so why was this situation not repaired under warrenty?

Never heard of a loose injector causing this kind of problem but it almost makes sense. You would assume the carbon is entering the tank through the fuel return line and possibly some blow-by at the injector could cause such a thing. Keep us posted as to what you eventually find. Have you considered installing a fuel filter on the fuel return line?

What have seen is the injector having a bad o-ring and oil getting into the return fuel line and turning the fuel dark.I have also seen a cracked head causing Coolant to return to the fuel tank. But that is an extreme situation.

On my 2003 international 4300 truck, we had a similar problem. Truck was going thru about 3 quarts of oil per hour of run time! Fuel in tank was turning black. Turns out some part in the high pressure fuel system was malfunctioning. Since the oil pressure is used in the fuel pump, oil was crossing over into the fuel return to tank. I forget exactly which part failed.

Loose Injector | Good Sam Community

33 Replies

chuckftboy
Explorer
Dec 18, 2015
Never heard of a loose injector causing this kind of problem but it almost makes sense. You would assume the carbon is entering the tank through the fuel return line and possibly some blow-by at the injector could cause such a thing. Keep us posted as to what you eventually find.
Have you considered installing a fuel filter on the fuel return line?
wolfe10
Explorer
Dec 18, 2015
Asphaltene
donfrump
Explorer
Dec 18, 2015
Tom/Barb wrote:
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.

No a loose injector would never cause this situation however I have to ask so why was this situation not repaired under warrenty?

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Loose Injector

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