On 4 Feb 2007 18:43:01 -0800, "Frogwatch"
wrote:

Years ago, I put an electric fuel pump in line with my mechanical pump
to help in bleeding the fuel system. When I turned the key, it would
run till the system was pressurized and would then stop. If it ran a
lot, I knew I had to bleed the system. It finally had the diaphragm
go bad so I replaced it but was unable to get an exact replacement.
The new pump runs ALL the time unless I turn the key off and if I
allow it to run all the time it gets hot. Did I get two different
kinds of pump? Was the first a "demand pump" that turns off when the
output side is pressurized? Neither set of directions said anything
about this.


I'm visualizing an old style mechanical pump once used for getting
gasoline to the engine.
A cam pushes a diaphram against a spring. Fuel feeds out while the
spring extends. No flow, no spring movement - no push from the cam
driven finger.

And I'm visualizing an old style electric pulse pump, where a solenoid
prodes the same push as the mechanical finger of the old mech pump.
The contacts don't force another pulse, til the spring returns when
fuel has flowed away..

But now, fuel pumps are often centrifugal and don't stop n wait.

Brian Whatcott Altus OK