Rear of block on passenger side leaking diesel on starter

Along with o-ring being worn out, it is also possible for the bracket that holds the fuel line in place (mounted to the block) to wear a hole in the fuel line after 100,000 miles plus. Thank you Valleyautotech for your input. Another thing to consider with the 7.3 fuel line, at the fuel filter housing on the front of the motor there is a drain lever on the filter cup that should be actuated at least twice a year to clear any settlement out of the bottom of the fuel housing. This settlement can cause the winter fuel heater to short and not work when warming your engine. But on the same token the o-ring on the actuator arm cannot be replaced and you must buy the whole fuel filter housing to replace it if it starts leaking.