I think you're running pretty much what I used successfully when we had a BFA. BFA is a great machine, by the way. A rugged beast that can serve for decades. We have a later model "KY" genset now. Nowhere near as nice.
The Facet-Purolator Pump Page shows many aftermarket types. I think you have the "Cube Solid State" type with Mr. Gasket's label on it. The one I had was a low-pressure that looked like "Cube" and was labeled "Purolator." I probably got it before merger with (probably takeover by Facet).
I didn't learn till after I installed it that ONAN specifies a low pressure pump that includes fuel shutoff. In other words, fuel can't pass through it when it isn't running. My Purolator pump wasn't shutoff but I never had any ill effects.
Nothing wrong with what you're doing. I can't see how non-shutoff makes any difference unless you're tapping fuel off another system that's running with pressure in it. There could be risk of the other system's pressure forcing fuel past the float valve in the generator when it wasn't in use.
Possibilities from where I sit are:
1. Aftermarket fuel pumps, in general, don't seem to be very durable. You may have gotten a couple bad strays, but
2. Parts are made in "runs" (batches).
3. Parts get distributed in "lots" out of those "runs."
4. Your store may have gotten their whole inventory from one bad "lot."
Look through the Facet-Purolator stuff and see if there's one you like the looks of better. Problem then will be finding somebody who actually has it. My guess is that only certain popular ones are stocked.
