Unless you are ignorant, you are already aware that sprinklers are not foolproof. Pulsating models are certainly not immune to this and they may begin to malfunction for you. If this is the case, there may be some remedies to the solution. One of the more common issues and the one that is going to be discussed in-depth here, is issues with the nozzle. Go ahead and lift the nozzle up and unscrew the seating screws to remove it. There is one of two issues that could be happening. On one side, it may be a simple matter of clogging. If not this, then it could be leaking.
Either way, you slice it, this can be remedied by removing any debris or dirt that is trapped inside the nozzle. To rid it, drop the nozzle into a bucket of warm soapy water. Once it has been submerged for around 10 to 15 minutes, begin to scrape out the dirt with an appropriate pointed tool.