I just put a walbro GSS340 In tank fuel pump in my denali. My problem is this, at wide open throttle my fuel pressure is still droping to like 53-54psi, I was under the impression that with this pump I should be between 59-61 at WO? In all actuality the pump really didnt change my pressure much from the stock one, this cant be right. At Idle everything is normal, 60-62psi but if I get on it the pressure drops as RPM increases. If anyone has any ideas please let me know. Thanks. 04 Denali 6.0L Kenne Bell @5psi

 

You should be able to keep a little better pressure than what you are seeing. But on the 2004 models, there's not much you can easily do to keep fuel pressure up under high boost loads. 5psi shouldn't be maxing your system though.

 

Anyone ever expirenced this? As soon as I get the fuel level back down i am going to drop the tank again and double check everything.

 

It sounds to me like you did not get the pump module put back together properly.

I am seeing 63 psi on my 2004 with 7-8psi on the stock fuel pump with the MagnaVolt Voltage Booster.

 

Try changing the fuel filter, it might be causing a restriction

 

Brian, Ya that is what I was thinking, however I cant figure out what went together wrong. I remember every step and cant think of where I went wrong, once I get the fuel level down i am going to drop it again.

 

Low silverdo, Ya I quess that is a possibility. only like 12,000 miles on the truck and the tank is clean as a wistle inside but who knows. I think there is something else.

 

Those o-rings can bite you every time.

 

I dont think the filter, which is in the sending unit is serviceable. On the '04 and up with the returnless fuel system, the filter is inside the sending unit. On the
'04 and up turbo trucks we do, we always change the pump and install 43lb injectors to make sure there is enough fuel.

 

04+ are returnless? Damn! Learn something everyday!