WHEN PARKED ON A GRAVEL DRIVEWAY THE TRUCK CAUGHT ON FIRE IN THE ENGINE COMPARTMENT. THE TRUCK WAS IN A RURAL AREA AND THE FIRE DEPARTMENT TOOK SOME TIME TO ARRIVE. THE TRUCK WAS A TOTAL LOSS. THE TRUCK HAD BEEN DRIVEN APPROXIMETLY 120 MILES THAT DAY WITHOUT INCIDENT. THE TRUCK HAD BEEN PARKED APPOXIMATLY 1 1/2 HOURS BEFORE IT SELF IGNIGHTED.