>>> YOU CAN RUN BOTH <<<
I would never trust an electric pump as my only means of fuel supply.
I do, however, have a Carter electric plumbed in a by-pass.
I have all the advantages of the electric pump, plus the dependability and longevity of the mechanical.
The electric only gets turned ON when it is needed.
I have a valved quik-couple that I can connect a hose onto to pump fuel from any of my three tanks into anything from a Dixie-cup to a bulldozer, whatever the need may be.
I also have a valved return-line bypass that allows me to transfer the fuel from any tank into any tank; this little convenience gets real handy whenever a tank is full and needs to be empty.
I can turn ON the electric to pre-charge the fuel system, thus negating any chance of air in the lines.
All that being said, on an IDI, or any diesel engine for that matter, you should NEVER have to bleed anything when all that is done is a filter change.
If filling the filter FULL does not allow starting, then you have a drain-back situation that needs be addressed.
Install a check-valve in the filter outlet and see if the next filter change doesn't go easier.
