It has pilot armor, it is clearly visible in the cockpit. None of the Brewsters had self sealing main wingtanks due to the nature of the wing/tank structure. It does burn/leak fuel when hit. One thing that might make it burn less easily compared to the Zeros for example is location and shape of the tanks. But from personal experience it burns/leaks fuel with similar frequency to the Zeke in which I usually go down from other damage.
Another thing that led to Zekes catching fire was also the location of the oxygen tanks, which were located behind the cockpit. Allied pilots were instructed to aim for this location as it would always result in an explosion that if it didn't either kill the Zeke pilot outright, would usually then lead to the Zeke catching fire.
ack-ack
