WHILE DRIVING ON HIGHWAY GOT A FAINT FUEL SMELL (NOT SEEN IN PAST). SHORTLY ANOTHER MOTORIST FLAGGED ME AND SAID HE SAW FLAMES UNDER THE CAR. I PULLED OVER AND EVACUATED VEHICLE. SMOKE AND FLAMES CAME FROM ENGINE. THE VEHICLE HAS BEEN MAINTAINED NO RECENT ENGINE WORK. CAR HAD BEEN RUNNING FINE WITH NO PROBLEMS.