Piper Aztec pilot reported right engine fire during engine start. FBO personnel extinguished the fire.

Narrative

Preflight showed no abnormalities. Started left engine and right engine with no issues. Engine indications appeared normal for both engines. Leaned both mixtures for ground ops and noticed no abnormalities. After approximately 2 minutes while obtaining ATIS and clearance; right engine stopped. I assumed I bumped the mixture and attempted a restart. During restart there was a pop and passenger observed flames. At the same time another aircrew started doing the ground fire signal. I executed memory items for engine fire on the ground and secured the aircraft and evacuated with fire extinguisher. Right engine cowling and asphalt under engine was on fire. Flames appeared primarily forward and inboard on the aircraft. Discharged fire extinguisher and of FBO fueler fueled arrived with stronger extinguisher. Airport ops arrived with ARFF (Airport Rescue and Firefighting). ARFF inspected aircraft and determined fire was extinguished. The aircrew that was giving the fire ground signal indicated fuel was spraying form the engine prior to ignition. Based on the stoppage of the right engine prior to fire indication I suspect a fuel line became dislodged leading to fuel starvation of the engine and the attempted restart with electric fuel pump introduced fuel to hot engine components leading to ignition.