The cap seals the fuel tank of the STIHL 180 chainsaw. It usually has a pressure-equalizing channel so that fuel flows freely to the carburetor. Manufacturer: EMAST.
Replace it if fuel leaks, the seal is worn, the body is cracked, or the saw stalls because of vacuum in the tank. When replacing, check the tank neck.
When replacing, clean the seat of dirt, oil and sawdust and inspect the neighboring parts: a worn unit often drags the others with it.
