I fear I’m experiencing a fuel pressure loss while in boost. Bank1 is going lean somewhere above 3psi confirmed by both wideband and O2’s. Hoping to test fuel pump tonight once I make it by sloworeillys to borrow a gauge.

Truck is an 08 5.3 TVS’d running around 6psi (impatiently waiting to swap the 3.6 for a 3.2 pulley). Truck appears to have the FSCM / FPCM by the spare tire. I’ve read that the FPCM complicates or eliminates the option of a boost a pump.

What is the best inexpensive way to upgrade the fuel pump? I’m not prepared to drop the $350+ for a new flex assembly as I just completed a 80e swap. Also I’d rather not chop up the bucket if I can keep from it. I’ve seen several installs of the 255LPH Walbro and mention of same or larger Aeromotive but not a lot when it comes to the returnless FPCM setups.

Set me up only want to drop a pump in once!

 

The Walbro 450 can be pulse modulated, from what walbro has said, but I havent seen anyone post up about if this is true or not by doing the install.

 

Hate to be the guinea pig when it comes to the joy of droppin the tank.
If the pump is as Walbro says compatible with variable input voltage and I stay returnless what issues would I have if its too large and how would I know? How about voltage requirements and the stock wires and the FSCM?

 

Not finding much info on the 450.
How about the AEM fuel pumps part number 50-1000 and E85 50-1200 shows voltage as low as 6vdc and around 320lph at 43psi but didn't see any reference to pulse modulation or returnless.
The Aeromotive stealth FAQ indicates they are not recommended for returnless systems but do support pulse width.

What are you guys running on your FPCM returnless systems?

 

Pump tested out around 60 while cold once warm dropped to just less than 50. Didn't see the pressure drop while in boost but also didn't see it rise while the RPM's and load increased.

Any thoughts to why it would start going lean out of the blue?

 

Intrested in this also

 

Well this is an older thread but yes you can use a 450 lph in a non flex bucket. I have a 07.5 gmt900 4.8 with a t76 pushing 10lbs and got plenty of fuel left.

 

Yes i know its an old thread. Its hard to find definete answers on the nnbs fuel system.

I wantrd to try and keep the stock returnless setup, supercharged 5.3 approx 500ish hp. What are the option on doin so?

 

Other than doing a flex fuel pump swap not really. Flex pump is good for about 600hp.

 

What did you do on your fuel system