Unknown cause of incident. Vehicle is available for inspection. Vehicle spontaneously burst into flames. No reproduction due to incident happening on 09/02/2022. Vehicle inspected by Fire Department and California Highway Patrol. No warnings or symptoms leading up to incident. On 09/02/2022 I attempted to help my wife that was stranded out State Route Highway 36 in her 2009 BMW 750 LI at the Van Duzen Grange. I had been hooked up to her car for approximately 10 to 15 minutes with my truck idling when she screamed, " Your truck's on FIRE!" I barely got myself out of the cab when a ball of flames shot through the dashboard. 3/4ths of the truck was consumed in fire in less than 5 minutes. Fire Department arrived approximately 10 minutes later and doused the fire. Everything in my truck was destroyed. My wife's BMW suffered severe damage to the front end.