Got your attention? lol Seriously, yesterday my bus did catch fire but all is good except unable to determine the root cause. I was really getting jealous just watching all the other busnuts posting questions and problems, so my turn.
Background
Bus was parked for a about a month. I started it, aired it up, then moved it from storage into a campsite on the ranch, about 300 yard, a short distance. Once parked and engine shut off, I exited the bus and the neighbor was looking at the bus.
As I went to greet him at the back, I saw some small light gray smoke from the engine compartment, similar to a couple drops of oil on a hot exhaust pipe. He mentioned something fell from under the bus, on fire, small, and immediately went out. I opened the passenger engine door and saw very light smoke and a small flame, about the size of a tennis ball.
Hold the laughter. It was small and weak, so I stuck my head in there to blow it out. Sort of worked but it was stubborn and did not die out but did not grow. I grabbed a fire extinguisher and gave a quick squirt or two. Very stubborn, it would die then pop up again but always small and not particularly worrisome in that it seemed highly unlikely to spread and under control but not permanently extinguished meaning there was some source for it to stay alive.
One last note is the frame rail was super hot. Yeah, my finger still reminds me.
Heat and fuel makes fire.
Pictures are attached. It is hard to get eyes on it, this is the right side of engine and the main frame rail and engine block are your references. There are hoses in that area, one from power steering going to front, some air hose, etc. I found a large bare electrical wire, I've not chased it but likely going to the starter. Maybe the power steering fluid was leaking then dropped fluid onto the bare wire then shorted to create the fire or there was a short that made the metal hot so it caught fire when some flammable fluid fell onto the frame rail?
https://photos.app.goo.gl/WzbE32GmQLBqBvC56 (https://photos.app.goo.gl/WzbE32GmQLBqBvC56)
Sometimes critters like to move in and add flammable ignition points when a vehicle sits, and they often also like to nibble wires. Perhaps the something that fell out was a blazing mouse nest or such, leaving behind an ignited patch of grease/oil in its place.
Dead short in main battery cables!!
Immediately disconnect all batteries, not the switch, take the terminals off to be sure!!
Common part of a professional bus refurbishment is pulling new heavy cables... most busnuts are gambling that the bare cable falls on a deep enough pile of perished jacket...
Happy coaching!
Buswarrior
Starter wasn' stuck on? Worn wire shorted out? Arcing at starter big wire and enough grease, oil and debris to get it going.
you guys are great. After some further troubleshooting, the heavy duty wire running to ground and the starter must be the fire source. I will pull it and replace it. Probably not bother running it inside the frame rail, plenty of place to run it outside and safely secured.
A friend of mine confirms the comments. He tells the story of doing welding in a vehicle engine compartment and how common it is for some grease to fire up due to the intense heat.
One other piece of the story is after a couple minutes of trying to stop it, i disconnected the starter battery bank and it did stop shortly after than. Not saying 100% but it fits the targeted source.
Will keep you posted in a couple days and hand out prizes if you had the right answer. :)
Pictures for the education of those who follow. Those cables will have some nastiness.
Happy coaching!
Buswarrior
Update - case closed.
I found a small big truck parts store in this little town. Super nice, super friendly, super service, super price to get a new 39" custom 00 battery cable made up, super quality job.
Luckily, it appears the damage was very localized to the area where the frayed cable was in contact with the frame rail. And I do agree the heat from the short ignited grease and the cable wrapping and the reason why it did was small and stayed small, and even though the bus was shut down there was so much heat on that rail, it kept the flame going.
@Marshall (https://busgreasemonkey.com/profile/Marshall) - I did take your advice and took that post block off and on this bus the block does not ground to the frame as it is not metal but a rubber type block. I did clean it up, the other cable ends, and post, etc.
I looked at the big cable that goes toward the front, 0000 and the lack of frame grounding off this post, it means that cable is the main ground wire. Where it goes, would take some research, crawling or reference to electrical diagrams.
To your point that the alternator is likely grounded on this wire, that makes sense now since there is no solid ground point at that post to the frame so the starter ground is directly tied into the same ground as a lot of other stuff based on the 0000 ground wire.
Given the bus was parked awhile, the battery was in full charge so the alternator was at max current on that same ground circuit.
If something changes I'll update. thanks all
https://photos.app.goo.gl/5mXwx5rGevi2BjGs5 (https://photos.app.goo.gl/5mXwx5rGevi2BjGs5)
https://photos.app.goo.gl/nLTDC1qadzUCPbCK8 (https://photos.app.goo.gl/nLTDC1qadzUCPbCK8)