Hi Guys,
There "is" a copper washer around the tip of the fuel injector. The tip of the injector protrudes into the combustion chamber a small amount. The copper washer is what provides the seal between the injector and cylinder head combustion chamber. If the injector isn't properly torqued in the cylinder head the copper washer will start leaking and allow combustion gas to escape around the injector and up the injector bore. Usually once the copper washer starts to leak you will have to remove the injector to allow cleaning the carbon and black "goo" from the injector exterior and injector bore. There is a flat seat in the cylinder head and the matching seat on the injector, the copper washer is "crushed" between these two seats. Both of these seats need to be very clean for the copper washer to seal against.
You can try just torquing the injector hold down clamp nuts, this will probably slow the leak down at least for a while. It is highly unlikely that the injector is cracked. I don't know if you can buy just the copper sealing washer for the injector from the GREAT dealers that frequent this site (hopefully one of them will chime in) If you have a specialty fuel injection shop in your area, you can probably find something that would work. I'm not positive but I don't think the copper washers used on banjo fitting are the same, they seem a lot harder than the ones used for the fuel injectors, could be wrong about this though.
Ditech