I believe there are o-rings that break down. Check with an injector shop. They may be able to cross match the parts. I had this problem in my duramax. I haven't noticed it in my ford 1210 yet.
Fuel injectors, with time, leak diesel fuel into the crankcase. This is a real problem as it breaks down the lubrication qualities of oil and destroys moving parts. If you have a copy of your service manual, it has a section on rebuilding injectors.