I'm getting things ready to go for my Procharger install. I recently installed a fuel pressure gauge and went on a test drive and noticed that my fuel pressure drops a bit at WOT and if I leave it there it will drop 9PSI. Is this normal for a N.A. motor to do? I'm running an Edel MPFI @42PSI.

 

Since nobody else has answered yet, here is the standard reply to your standard question: What year is your truck? Are you running a return or non-return system? Are you using the stock regulator?

 

My truck is a 90. I am running a return system. It's the Edelbrock 3562 MPFI conversion. I'm using an Aeromotive Adj. FPR. It idles @42PSI

 

It means you probably don't have enough pump, filter is clogged, something like that. When you transition to WOT on a NA combo, fuel pressure should rise roughly 10 psi from what it is at idle and hold steady. If the pressure is dropping, supply isn't keeping up with demand.

You DEFINITELY want to address that before boosting that big motor!!!

 

Is the regulator indexed for boost? Do you have your FP hot-wired for power from the back of the alternator? Are you still running an in-tank pump or an external one?

 

I'm not boosted yet (I want to address this first). I'm using an Aeromotive LT1 Adj. FPR. My SC kit has an FMU and I will end up taking it off when I get my motor dyno tuned and a new PROM burned. The fuel pump is in tank and wired stock. It's rated at 255LPH.

 

I had similar issue, and it was my fuel pump. It was a 255 as well that had never seen boost. It just took a crap under wot.