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Posted by Chriscase [76.224.243.62] on Monday, May 17, 2010 at 16:13:56 :
In Reply to: Fuel Pressure from stock fuel pump? posted by Galen [156.80.4.2] on Monday, May 17, 2010 at 13:50:42 :
I think 4-5 is plenty. That;s the max a mechanical will do, static. Less at the speed of a running engine.
The diaphragms will dry out and get hard. slowing down the movement- remember, it's only the spring pressure that pushes the fuel, the cam returns the pump- the sucking motion into the pump.
On the pumps with two springs, the stronger one pushes on the diaphragm, the weaker one is an anti-noise spring. You need calipers or mic ti tell the stronger one is just a few thou thicker wire.
When rebuilding, let the spring push the diaphragm, don't try to hold the motion in the middle. This will allow the full motion without having to stretch the diaphragm. The normal position of the diapragm is at one end, if under pressure, or the other end if left parked so long that all the gas has evaporated out of the pump.
I make my own diaphragms from Buna rubber. I make the screw holes oval, to allow the diapragm to pull inward under spring load, as above. I've got some spares, $5 each, if your pump is rebuildable. email me.