the engine feedline does hold pressure, however, it will slowly dissepate when sitting or turned off. Not as fast as you say though.
If it were me, I'd drop the tank and re-check my work, if everything looks like it should, then it's probably the pump. As long as this is the only area you touched, it's safe to assume that's where the problem lies, although, not a guarantee.

 

What do i do with the pump? that was like 123 dollards that is down the drain? I don't think they would take it back.....

Nate

 

if its faulty, return it, and get a new one, shouldn't cost you anything.

 

did you replace the sending unit, I had to replace both (sending unit/fuel pump) on my 2000 Silverado, it was only reading 5 psi when it was supposed to be reading 55 psi, it sounded it like it had a built motor with a healthy cam when I would crank it up, but when it would start to idle by itself it would sputter really badly

 

The engine/pump/psi are all fine when the engine is running.

Nate

 

The check valve is part of the pump. I have noticed my pressure bleeding off lately too. Your prob is either the hose connecting the pump to the module or the pump itself.

 

It sound like the check valve. Mine does the same thing and I know for a fact it's my check valve. I just turn it to the on position, wait about 2-3 seconds and it fires right up.

 

It sounds like the regulator is bleeding off fuel instead of keeping it up at 58psi. Well, you didn't touch the regulator, so we have to assume thats not the problem. You did however mess with the pump and hose that connects it. My bet is that its the hose or the clamps you used to connect the hose. I bet there is a leak and at 58psi its bleeds off in the 3 or 4 seconds. Drop the tank and check that hose and clamps.

 

does anybody know where i could find the GM part number for that plastic pump hose thats in the tank??

thanks,
Nate

 

Its that clear accordian looking hard plastic hose.