Hi im having trouble with a 2000 chevy blazer . at first it had really low fuel pressure so i changed the regulator under the plenum no change. So i went ahead and got the pump changed that and now it has 90 psi at schrader valve.
What can be causing this bad regulator even though its brand new or the injectors?

any help would be appreciated thanks

 

Do a timed leakdown test. See here.

Different motor, same in principle...

 

Running or not running. Try key on engine off. dont start

 

My bad i forgot to mention that. ok So after i wrote this earlier i went ahead and took the plenum back off put my old regulator on there key on 62 key off 55 . after i got it back together it runs but it still goes pretty high im going to check it cold in the morning .
it did have black smoke coming out of tail pipe but after i switched it it definitely changed something i also blew the return line out when i changed regulator i took the line off pump can this pump have to much pressure for a regulator to work. or

 

Well this morning i fired it up started smoking black. went for a ride about two blocks from home i stepped on the gas as i did that the engine died i rolled into someones drive way i knew the person so i looked under the blazer on the fuel pump for the high pressure the plastic fitting broke flush off and the line was sitting there with the plastic piece. so now im needing another pump lol.

 

Black exhaust = fuel.

Do a timed leakdown test. See here.

 

Fuel pump Solved the problem i ended up putting the lines vise versa for the evap hose and the return line lol ,