25-02-2015, 05:20 PM
That's diesel leaking from the injector over a long period of time, basically coal. The only time I've experienced this, I spent a good hour pulling the injector out, and a couple of hours after that chipping away all the crap. Make sure you keep it from going into the cylinder in any quantity, and good luck!
Welding and fabrication projects undertaken, contact me for more information.