<VV> Fuel pump pressure

[Smitty]

wondering if the spring has that much to do with actual pressure?
I would think those button valves do more for pressure?
I have put several replacement covers on ( chrome or correct AC ) with no
known change in pressure I have a test gauge made by putting a tee with
small fuel pressure  gauge on a left fuel line.
regards, Tim Colson
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Smitty Says;   Tim the spring and only the spring is what controls the
maximum pressure of a pump.  Maybe I can "splain" it in a thousand words or
less.  You go over the top of the hill and start down the other side.
Throttle plate is closed and the engine isn't asking for any gas.  The float
in the carb lifts up and closes off the fuel inlet so the pressure in the
lines starts backing up to the pump.  Up to a point the diaphragm is still
fluttering and through the use of the valves trapping pressure, is taking
smaller and smaller bites of fuel until the backed up pressure overcomes the
spring and compresses it.  Finally if we take this scenero all the way the
pressure has overcome the spring all the way and is holding the
diaphragm,(and thereby the pump pushrod) off of the cam.  Oh it might be
brushing it slightly but not really pumping.  You get to the bottom of the
hill and need the car to keep going so you press the throttle. The throttle
plate opens and the venture starts drawing gas, the float drops and allows
fuel to come in.  the pressure drop in the lines allows the spring to push
the diaphragm down, and the pushrod starts pulsing on the cam again.
Through it all the spring is the only thing maintaining pressure on the fuel
lines.  
For you folks who like to pick nits, I understand this is not an all or
nothing operation, the way the fuel is controlled.  At low speeds and low
demand the diaphragm will be held in the almost "all the way up" position
and it will be constantly shifting from the cam contact position to the "no"
contact position.  The spring will be maintaining its full capable force on
the diaphragm at all times, be it 2 lbs or 4.5 lbs or 7 lbs.