Fuel Press. Problem

[Hawaiian5.0]

Have a new < 2 mos. old Walbro 255 in-tank and Adj. Kirban FPR.
Problem is I'm not getting the fuel spike when the gas is mashed. At idle I'm only getting 26-28 PSI and it drops 2-3 PSI when I get on it. I thought the FPR was faulty since I baught it used but I swapped in my stock reg. and no change. When the key is cracked, my fuel guage jumps to 40 PSI then immediately drops to almost 10 and doesn't hold the pressure like before. Is my pump already bad? Lemme know what you guyz think? Thanks alot!!

 

[TheUser]

the Kirban is adjustable right? Adjust it w/ the car idling and vac off. I think stock is 38 vac off, so I'd start there. I believe it reads lower w/ vac on...for some reason, mine doesn't, but regardless, I believe it's supposed to. In any case, I think 28 is too low. have you changed your fuel filter? Have you ran some injector cleaner? Might try those as well. Wouldn't hurt. Hope this helps.

 

[BAFMustangGT]

Most likley the pump, otherwise the regulator would show a good reading and hold it there.

 

[Hawaiian5.0]

Thanks guyz! The fuel press. was adjusted and then 1 day it just dropped. So I guess I gotta pick up a new pump again! Thanks!!!