What is stock fuel pressure at idle, and what should the fuel pressure look like when reving up. Would a walbro 255 change the fuel pressure or just the volume.

 

The walbro is a higher capacity pump than stock, therefore its trying to pump a larger volume of fuel at the same voltage. Problem is, its trying to pump the larger volume through the same size orifice (FPR) therefore, fue pressure goes up! Fuel pressure goes up, more fuel is pushed through the injectors for the same duration opening time.. Thus... AFR goes down (gets richer)

on an N/A and turbo Idle Fuel pressure is 28.4 PSI with the hose off the FPR (simulating FWO throttle) it should be 39.8 (or with a jumper wire installed on the FPR solenoid on the tII's)

 

hmm mine goes up to like 40 psi when I first start reving, but once it gets to like 3500 rpm it starts to drop. it drops all the way down to like 6psi and then the engine cuts out... any ideas what could be causing this, maybe stuck fpr??

 

anybody?

 

I believe that your problem is the FPR...

I went with a Weber Setup now but before I did i used a Malpassi Fuel Pressure Regulator that is simply the best and any racer will tell you how good they really are. Murrays Speed & Custom carries them for about $80.00

Here are two pics so u can see the FPR.. Looks like a flying saucer to the right