The Purpose of a Primer Bulb
- A primer bulb sends gas to a small engine's carburetor when pushed. This enriches the fuel and air mixture with more fuel during engine start.
- A large internal-combustion engine sends fuel to its carburetor or fuel injector with a fuel pump. Small engines don't have a fuel pump. Fuel for starting the engine must be delivered manually by pushing the primer bulb.
- The primer bulb will be directly attached -- or very near -- the engine's carburetor. Pressing it with your finger produces the pressure to send fuel to the carburetor.