Do you prime the fuel lines before starting? as in, turn the key til the fuel pump does it's thing and stops and then turn it further to start?
I installed an 044 intank and it has No non return valve so when the car sits for a while, the fuel seeps back into the tank.
If I try to start it straight away, yes, it takes 3 to 4 seconds to start but if I prime the lines, it starts right up, cold or warm.
This rarely happened with my stock pump but it didn't seem to have a valve on it either.
I just recently bought a non return valve to try stop this and will slap it in soon.