7% diesel in oil detroit 60 series 12.7

You can just take the turbo exhaust flange off, or the flex pipe to check for raw fuel. Maybe the fuel pump is leaking into the compressor. I don’t know if it’s common or not

 

Before an oil change I would poor a gallon of kerosene in the oil which is like diesel and it cleans out some gunk build up

 

Why would you do that? He's already at 7%, which means he's already got nearly a gallon of diesel mixed into his oil.

 

Where does the fuel pump mount to? Directly to front cover? Wonder if the input shaft seal is leaking?

 

Fuel pump mounts to the back of compressor, geared to compressor. They’re very reliable. Usually will seep from a weep hole in the bottom, when going bad. If it’s plugged up with debris though it won’t. They do leak into compressor sometimes. It’s rare but can happen.

 

Need to put some dye in the fuel, take valve cover off. Plug the return line.Take the fuel line off the fuel pump, and pressurize the system. One of the injectors is probably leaking.

 

Is the oil level rising with the 7%? A gallon is a lot and if the engine isn’t consuming any of it it should be overfull all the time.

I’d change the oil and go 5,000 miles and get a sample. Watch level and see if it rises above the mark you filled it fresh at. See what it tells you and go from there. If nothing go another 5 and test again. Maybe that engine just doesn’t like the oil going that long.
I’ve had samples tell me fuel in oil that I couldnt find. I even poured expensive diesel leak dye in tanks at fuel ups and that wouldnt show up under a black light on the dipstick or anywhere. Level never came up but never went down either.

 

Cummins allows up to 5% for the n14 per the online manual. So if the specs are similar for Detroit you're not really too far off the max

 

The older NH mechanicals could run up to 10% if they went 10,000 intervals. That is what messed me up 25 years ago. I never sampled anything and then when I did I saw the high number and I freaked out and started going down that worm hole. Some Cummins old timers told me it’s normal don’t worry about it. Just change the oil a couple thousand sooner. Oil on the old ones hardly ever gets black in 8,000 miles unless it is worked hard because of this.