Refer to figure.
A fuel primer is a small hand pump that delivers neat fuel directly into the induction manifold (near the combustion chamber) or the inlet valve port, providing extra fuel for the engine starting.

It should be used before starting a cold engine to ensure the presence of fuel vapor (priming a warm engine is seldom necessary).

Fuel injection systems do not require primers.

NOTES:

• As the primer injects fuel into the manifold, you can put fuel into your engine if it quits because of carb icing. Aside from the fire hazard, excessive priming should be avoided because it washes lubricant off the cylinder walls.
• It's crucial to remember that primers should be locked in position during flight. This avoids excessive fuel being drawn into the cylinders, especially at low power settings. Such a situation could stop the engine because the fuel/air mixture is too rich. By following this guideline, you can ensure a secure and controlled flight, with the fuel/air mixture at the optimal level. Priming can also be done with the accelerator pump.