Caterpillar has stated that hold down bolts for the fuel injector should not be reused on engine models 3116, 3126B, 3208, 3306B, 3306C, 3406B, 3406C, 3406E, C-12, C-15, C-16 and C15. If the hold down bolts are reused, damage may occur.
When you service the electronic unit injector, replace the hold down bolts. If a washer is present on the fuel injector hold-down bolt, remove the washer and do not replace it.