Heres the question.
My car takes time to build up to 6psi with a carter external electric fuel pump. Whats wrong with it? Why does it not build pressure instantly?

Alright so heres the story.

I have a carbed 388 in a car that originally came with a 305TBI. I kept the in tank pump and used a mallory return style regulator. I was never able to get a consistant fuel pressure it was always jumping between 5 and 7psi. I left it like that and continued with other projects on that car.
Then one day I started it and went to give it gas (while in drive) and it died. I popped the hood and saw I had ZERO fuel pressure. I took off the inline filter thinking that it might have been clogged, took off the regulator, tried everything. Nothing worked no pressure from the intank pump. I had a spare carter fuel pump lying around, so I hooked it up and it would build up to about 3psi but not anymore then that. I tried to blow compressed air through the fuel line and could not.
Just yesterday I took out the intank fuel pump and put in a straight tube with a strainer at the end.
I rehooked up my Carter external electric pump and now it eventually builds up to 6psi (over a minute or two). I have the pump hooked up to a switch. On other cars ive seen, i noticed that the second the switch is turned on it brings it up to the correct PSI almost instantly. Why isnt mine? I am not using the regulator with the carter pump.

Any suggestions?

 

Take out the in-tank electric pump.

 

I did take out the intank pump. I have a feeling that I ruined my carter pump by running it with my intank pump and now it doesnt work properly.
Today I put a hose going from a spare gas can to the carter pump to eliminate any chance of line kinks or clogs. Still does the same thing, eventually builds up pressure. I think I need a new external electric pump.

 

Sorry, I was reading in a hurry and skipped that line.

I'd guess you need a new pump.