The firing pin in the early rifles models is in two pieces, a front and a rear one. Paulo is correct when he surmises that when the front and back pins are not aligned the rifle is unable to fire. The rear part of the firing pin is held down by the spring you see in the schematic. The 'L' shaped piece on the spring fits into a slot cut at the rear end of the front firing pin. The end of the spring bears down on the shaft of the rear firing pin. When the lever is closed the locking bolt pushes upwards on the rear firing pin thereby compressing the spring and because the firing pins are now aligned the mechanism is in battery and ready to fire. It is this safety mechanism that in part contributes to the name "Marlin Safety". The spring will break on occasion or gets lost in disassembly but is easy to make and replace if one can't be found on the internet.I am cleaning up an early 94 for my stepson. The bolt was siezed up so i soaked it in PB Blaster and when i disassembled it, I noticed the firing pin was broken. I logged onto Numrich and looked at the schematic and see there is a “firing pin spring”. Where exactly does this go? I can see no spring on the bolt except the extractor, which obviously has a spring.
Part #17 on this schematic