I have an autometer FP Gauge,

and it acts funny...

I have 2 walbro 255's
60 lb injectors

what Fuel pressure should I see at idle?

30 psi or so?? Thats where it sits... then when I go down the road it hovers around 25psi... and shakes..... when I go into boost it does not move until I hit 13 psi boost or so... then it jumps up to 45-50 or so..

but when I am putting a tune in my truck via my xcal2, it pegs at 50psi fuel pressure... but when I am driving and do like 4-5 psi or even up to 10 psi, it does not move... is there any other way of testing this without getting a mechanical one?? maybe a ground on it is bad? how can I tell if its the gauge or if its the sending unit?

it should be 30 psi at idle and then 1 psi more for every # of boost right? more or less???

 

sounds like the sending unit is going out.

 

I was getting the same readings on my AM fuel pressure gauge after I installed the Aeromotive fuel rails. I tried everything and the only thing that fixed it was bypassing the resistor. But that won't work for you unless you have an adjustable FPR.

 

Well, I did bypass that resistor, and boy let me tell ya... I got all the power back that I am lacking... kind of wierd.. I think my resitor is going bad... or the tune is not quite right for it... I took the resistor off and spliced the wires together and boom... 60 psi fuel pressure at idle... whci is not a good idea either... I am ordering another resitor...

I just prooved that my pumps work, and my fuel pressure regulaotr is working..

either this resitor is bad, or its not properly tuned for the bigger maf I have I guess.... From what I am told, this resitor has to match the MAF that you have in the vehicle... I have a BA2800, and i think it needs tuned for it...

this is what SCT told me...

I don't think I am going to run my pumps like this very long... I don't think the fuel pumps are designed to run like that are they? also would this hurt my injectors after a while?

 

It sound's as though your regulator isn't working, I bypassed my resistor a few year's ago. I saw @ 38 at idle and 50 under boost, increasing with boost to almost 60 psig. I have an adjustable fuel reg, I'm assuming you have the same???
Bryan

 

nope.... stock regulator...

how could it be the regulator?

i unplug it and nothing happens....

this fuel pressure thing is ticking me off... and since it is welded to the fuel rail... I have to pull the whole fuel rail off.... and since I have a whipple, thats a little hard to do...

 

and the regulator worked fine before my whipple upgrade... so the only variable is the tune...

I do not know...if I see 60 psi then the pumps are working...

all i know is that the maf directly affects this resitor, since I have a different maf, i think the tune has something to do with it not wokring right no? is that not a safe conclusion?

 

Mines does what you are saying. Mine doesn't bounce around but around 30-32psi at idle and at wot it hesitates a sec and hit 40-45psi.

I also have twin 255's 60's stock reg.

 

By-passing the regulator makes it a totally mechanical system, not controlled by the ecm. I would def'n get a new resistor if you have no way of controlling the pressure (ie adj reg). Unplugging the hose off your regulator will not change anything unless you're under boost.

 

I would see if Auto Meter will swap out your sender for a new one. That way you can check that off the list as a possible problem.

 

nope... it was in the tune... figured out how to change when the fuel pumps kick on different duty cycles... and match those with the fuel curves...

Rick at amazon is AWESOME... truck is starting to come alive... He keeps bugging me to get a better heat exchanger though.... he told me that If I want the 15 degrees.. I need a heat exchanger to do it.. HAHAHA...

 

glad to see you got every thing figured out and working propely.