Hi, I have a Toro GTS self-propeller walk-behind mower. It has worked great for 7 years. The last time I tried to use it, it began to die every minute or so. I experimented, and realized that if I pump the fuel primer bulb, it will stay running. What problem does this symptom suggest? Do I need to take it apart and clean out the carburetor? Thank you for the benefit of your knowledge.