You have it all right -- as far as it goes. But it is the spring
which supplies the force to push the fuel to the carburettor. And if
the spring is broken, the remaining part presses harder than the
longer unbroken spring which the factory provided.
So the fuel has no place to go unless the [excessive] spring pressure
overcomes the needle valve.
Donald.
> Date: Wed, 08 Oct 2003 17:00:46 -0400
> From: Douglas Braun <doug@dougbraun.com>
>
> I think you have it backwards:
>
> The lever arm which is operated by the camshaft pushes the diaphragm down
> against the spring pressure, sucking fuel into the pump chamber from the fuel
>tank.
> When the cam lobe stops pressing against the lever, the spring is free to
> press the diaphragm upwards, expelling the fuel out to the carbs.
>
> If you a pump with the little priming lever, you can get a good feel for the
>way
> the pump operates. Pushing the lever down sucks fuel into the pump,
> and when you release the lever, it rises, and fuel is squirted out to the
>carbs
> (or out onto the floor, if the carbs are missing :-)
>
> After the carbs have filled up, the level will stay down after you press it,
> because the fuel has no place to go.
>
> Doug Braun
>
> At 02:10 PM 10/8/2003 -0400, you wrote:
>
> >Simplest mechanism for increasing fuel pump pressure (while
> >simultaneously decreasing the volume available) is for the spring to
> >break. The shorter spring has a higher spring rate than the longer
> >(unbroken) spring and can increase the pressure up to double.
> >
> >HTH,
> >Donald.
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