A couple of things:
Fire Up, the fuel doesn't explode, if it did you would have detonation. It burns, ( as a fireman you should know that ) just kidding.
Brett, There is probably a small amount of fuel injected during the braking cycle. The reason I say that is before computer controlled engines, when we had the mechanical 'pt pumps' we were told to never completely release the throttle on A long downgrade ( before jake brakes ) because it could score the cylinders if allowed to run dry. No scientific evidence, just an old trucker who got lots of miles from a Cummins engine.