We just recently had about 230 tons of crushed stone (I call it slag) laid down on our dirt road (about a mile long). I was smoothing it out with my Duragrader as I've done for the last 18 years, and after about 30 minutes or so, I started smelling burning. There was a lot of gray dust from the rock (extremely dry), so I didn't realize it was from the tractor. I just thought someone was burning a field or trash somewhere. I kept looking around for where it was coming from, but couldn't find it. Then I realized it was coming from the tractor as it got a lot thicker and smelt odd. I thought it was overheating smoke, but then I saw fire flashing out from under the fuel tank. My thoughts were that I didn't think diesel would explode, but then again, I wasn't going to hang around to find out. I didn't have my phone and was about 3/4 mile from the house. Nothing at all around to put it out with, so I started walking back to the house (a neighbor that lives closer was at a funeral)... about the time I got where I had to turn and wouldn't be able to see the tractor any longer, I looked back, and all I could see was black smoke. I knew it was a goner, and there would be nothing anyone could do. Even if I'd had my cell phone with me... by the time the volunteer fire department arrived, it would be too late. It was too late, even within a couple of minutes of me getting off the tractor. The volunteer fire department did come and put out what was still burning, and then I had it towed back to the house.
Not sure what caused it, but we all figure it must have started leaking somewhere under the fuel tank and ignited in some fashion in that area. It may be difficult ever to know the exact cause. I checked where it was parked, and I did not see any evidence of a leak. I don't think diesel is that easy to ignite, hence why I was not too worried about it exploding, so what could have caused it really puzzles me.
The fire department said they wouldn't be able to determine it. I'm sending pics to State Farm, and my insurance agent said they might not send anyone out to look at it once they see the pics. They may send someone for the salvage.