I guess I've never really thought of this but it is quite important. If the engine driven fuel pump fails and the engine quits, will the engine automatically restart if the electric fuel pump is switched on. Or wouldy ou have to prime/start in mid-air?
If the prop is still turning and the magnetos are still firing, the engine should restart as soon as fuel flow is restored, so I'd say yes. It's a different story if you already went through the feathering procedure and everything, at that point you'd have to engage the starter for a while before you could get the prop to unfeather and the engine to start.
Some of the fuel injected engines may take awhile to get going again, but when aircraft are certified they test them to make sure they restart within so many seconds after fuel flow is restored. That is why most aircraft with electric fuel pumps have the pumps turned on during take off and landing. You don't want to chance a mechanical fuel pump failure close to the ground. Enroute it is not a big deal, just turn on the electric pump and everything is fine.