One of my injectors on my 4-108 was leaking, but it was leaking from two locations.
The first leak was where the injector meets the
head. There was a small
compression leak. The evidence was tiny bubbles that would appear while the
engine was running. Also, over time, there was a buildup of carbon on the
head next to the injects.
The second leak was on the return line banjo fitting at the top of the injector. That seeped a tiny amount of fuel with the
engine running.
Both
leaks were stopped with new copper crush washers, one at the bottom of the injector and two more, one on each side of the banjo fitting.
As an aside, in a pinch I bought the 80 piece copper washer set for $3.99 at Harbor Freight and those washers worked. They're still being used today.