lomapaseo
For the PW4000 installation, reasonably sure there isn't any fire detection in the fan cowl - and I'm certain there is no fire extinguishing ability (not that it would help with the cowl missing). Fire detection/overheat/extinguishing is all in the engine core - not the fan cowl. For engines where the gearbox is located on the core, the fan cowl is a "flammable leakage zone" (oil and hydraulic fluid) - by design there are no ignition sources, so no fire detection needed.
Edit - I see Dave T beat me to it...