Dropping Fuel Pressure

[Catoboli]

ok my problem is that my Fuel pressure isnt at the normal 40psi. it started out at 40psi then i started doing some tuning runs for my EMS and noticed my FPG read 30psi then a few minuts later it was down to 20Psi i checked all my lines and the FPR for leaks and nothing i have no clue as to why it droped. any ideas

The Fuel Pump is a brand new Walbro 255 HP
other fuel mods- AEM Fuel rail, AEM FPR, -6 an Fuel lines, & K&N Billet Fuel Filter

 

[danl]

What is your battery voltage when the FP reads low? Where is the fuel pressure sending unit tapped? What is the manifold vacuum reading when you are taking FP measurements?

 

[DSM Storm]

Did you install the pump correctly? Can I assume that you didnt forget to install the rubber O-ring in the fuel pump feed line?

Storm

 

[NOSLO2PT0]

Did you happen to hook up a vacuum line to the AFPR as well?

 

[16g-95gsx]

Define the "normal 40psi" as most set it to a base of 43psi, which under full vacuum is closer to 35psi or less depending on if you have aftermarket cams.

20psi is QUITE a drop, do your logs reflect this as well? Could it possibly be a faulty gauge? As someone else mentioned I'm curious what the battery voltage was during all of this.