I've been tuning the truck for the new front mount and cannot get the AFR spot on, it keeps jumping around. I don't like absorbing other problems into my tune to compensate...so I checked out fuel pressure, and its all over the place. Most times including idle and cruise, it stays around 43-45psi. At WOT it varies from around 45-55, but it is never constant. There's a 10psi fluctuation at least every second. I'd guess fuel filter first, but since it only delivers 43psi at idle, I'm not so sure. I haven't heard of any issues with them...is the in-tank regulator going out?

 

Do the nnbs use some sort of pwm on the pumps? I thought I remembered reading something about that...

 

Pretty odd. I know the failing stocker on my old 4.8 set up, couldnt keep up but would drop very linearly at WOT. Enough to were I left it that away and still ran an OLSD tune with no problems.

IIRC a thread on here said the NNBS pumps were only sold as a complete assmbly

 

I know the newer Vettes use a variable output fuel pump. I would like to know if our NNBS truck have made this switch. My 09 also has a variable output alternator and I'm curious how that could effect the fuel pump output.

 

upgrade the fuel pump?

 

Equipped with Variable speed fuel pump to the best of my knowledge I'll check on alldtata in a bit for you.

 

Not as easy in an Avalanche