Spent 3 days chasing a fuel smell on a King Air 200 before I found the real culprit

Been there with a fuel smell that turned out to be a leaking o-ring on the fuel sump drain valve, not the obvious stuff like lines or injectors. What saved me was pressurizing the system and watching with a bright flashlight while a buddy stayed outside the wing, that way you catch the tiny weep you'd never spot on a normal walk around. Sometimes the smell is coming from way further back than where your nose points you.