primer bulb

[izu]

What causes the primer bulb to get firm when its pumped ??

 

[Plainsman]

Re: primer bulb

There is a one way valve in the bulb. Also the diaphragm in the fuel pump, you need both to work right in order for the bulb to get firm.

 

[izu]

Re: primer bulb

I thought that when the fuel bowl is filled from pumping the primer bulb the float causes the inlet needle to close which results with the bulb firming up. Isn't this true. The diaphragm only exerts force when the motor's running due to alternating high and low pressure.

 

[Silvertip]

Re: primer bulb

The purpose of the primer bulb is to ensure the float bowl in the carbs is full prior to starting the engine. As fuel is pumped into the bowl, the float rises which closes the inlet needle and seat thus shutting off fuel flow. Hence the primer bulb gets firm as you can't pump fuel through a closed valve. So, Izu, your observation is correct.