I don't know about the Edelbrock pump but the Facet pumps as shared by Kenth allow flow-through when they are off. Edelbrock is probably the same.
Here are the Facet pumps (multiple lines) that allow flow-through:
https://www.pegasusautoracing.com/gr...ID=FACETSIPHON
I don't know how much of a restriction they will introduce, but it won't be zero. So these pumps may not make sense for high HP fed by a mechanical pump. For my car, unlikely to be an issue. I suppose you could always leave them running as long as they flow enough to support your engine.
These solenoid-style pumps apparently have relatively tight internal tolerances on wetted parts so they recommend a pre-screen filter. Facet sells a 70 u version that looks just like the filter with the Edelbrock pump. I don't like the setup using a rubber hose in a fuel line, so if I use a filter, it will probably be something with NPT fittings on both ends, like this, assuming the mesh is coarse:
The Facet pumps (at least the Cube line) can also be configured to block flow when they are off, but that wouldn't make sense as an inline primer for a mechanical pump:
https://www.pegasusautoracing.com/gr...ID=FACETSIPHON
Either the "Posi-Flow" or the "Cube" lines should work as a primer pump. There are more options available on the Cube line and they look like they are built well. I like the ability to choose max pressure and the claim of "self regulating". I think any solenoid pump will be self-regulating when dead-headed, but the range of available max pressures on the Facet line is more comforting than a generic claim of "5 to 7 psi" on many of them. I am squeamish about over-pressuring my carb and causing it to flood. This is apparently a common concern with mechanical pumps that also claim to have a 5 to 7 psi max but are then reported to deliver 10.
Mike