Folks - most likely this 'spray' is water from his cool suit system. It's little more than a glorified water cooler/ice chest inside the car with a pump and circulation system
He sat still in his car for a bit probably because he was on his radio telling his crew he crashed hard and would need a ride to the pits.
One of the first things you do as a driver after a crash (after you radio in of course) is cut the master power so that, among other things, your fuel pump shut off. Not sure Jr. did this. That could be becasue he was on the radio yakking when he should have been shutting down and extricating himself from his now useless vehicle.
I raced for years, and worked as a corner worker for more years than i raced. Fires like Dale's are rare. Somthing broke (like tubing) in my opinion and punctured his fuel cell. A simple ruptured fuel line would not feed a conflagration like that. (unless the fuel pump was still on of course)
Thanks for the info.