This is from Mr TK on that issue
by TK on Thu Jul 02, 2009 9:42 am
Which F-4 are you having problem with? Later model F-4 are more protected than earlier models, for example.
Fuel leak will only happen on unprotected fuel tanks, A-10 have self-sealing fuel tanks so you're not likely to see fuel leak situation on that. Try older aircraft if you want to see fuel leaks.
Individual fuel tanks and engines has its own settings in regards to fire extinguisher. Usually, wings tanks are not protected (I guess theory being that they'll be empty by the time you get to the battle, while fuselage tanks are. Also, the engine fire depends on the engine temperature, if you had it running hot all the time, then its more likely to catch fire (and not extinguish).