This happens when the engine is flooded and the engine is hydraulically locked. Pulling on the pullstarter while the engine is in this condition will break the pull starter  cord or damage the engine. Remove the glow plug and pull the pullstarter briskly several times (do not pull the cord out more than 12”). It’s good practice to check the glow plug/glow starter for a bright glow while the glow plug is out of the engine be careful not to burn your fingers). Replace the glow plug and washer, and the engine should be ready to start.