Best thing to do is just wire it direct through a fuel cut off, that's what I always do.
Pretty much all efi prime on cold start but NEVER on hot start, it is to wet the inlet to assist with quick starting, rather than churning away on the starter.
I had to triple my prime time on my ecu with the really cold weather/snow.
This is normally allied with cranking enrichment and enrichement turns, ie how may turns it stays in super rich mode, it then goes onto the normal map with the cold settings added to it.
The best thing like I say is just run continuous, it has a return so always at the right pressure anyway.
tabetha