first off id like to thank parish hes been helping me a lot with tunning this thing. i got it to drive fine when its not in boost my ltrims are slightly positive i could be a little more rich....but heres my problem im logging on atap to see where my 02 voltages and Ltrims are so i need to get into boost, but when i floor it as soon as my fuel pressure gets to 58 it starts to drop back down rapidly! like close to 40...35...30 thats NOT GOOD!!! especially when in boost... why does this happen? i thought it was the ATI FMU and i tossed that out and it still happens? my setup is : aux inline pump,42lb RC injectors, stock fuel pressure regulator (could that be it?), ati P1sc stock boost, ASM LTs, and a flowmaster... i also keep missfiring and my plugs are chalky ashy white...lean right? but my ltrims tell me diffrently... could that chalk build up cause my plugs to foul out and cause the missfire? BTW i have NGk tr6 in there.. but my real question is why does my fuel pressure drop back when when it reaches 58 i am stumped and frustrated

 

what are you reading at Idle for Fuel Preasure ?
Is you Voltage dropping at WOT not powering the inline pump ?
did you Change your fuel filter when you did the install ?
Your grounded well with the relay ATI sends with the fuel pump ?
I'm thinking its maybe a blocked fuel filter not alowing you to feed it
Well let me know when you check those things
good luck
jim

 

if your ltrims are not maxed out at +25% or -25% then most likely your part throttle a/f ratio is right at 14.7-1 like it should be. that is what the ltrims are doing is making the a/f ratio perfect. we are trying to get them close to 0 so there is more room for them to float around should they need to and we are trying to get them just a little negative so they dont effect our tuning when we start the WOT tuning. it would be nice if you could send a pic of one of those plugs.

figure that fuel presure problem out before you do anything else, i vote for some electrical problem to the inline pump.

 

I had a similiar problem with fuel pressure in my Camaro when I had the Procharger inline pump installed. The problem was that the pump had went bad and was becoming a HUGE restriction. If I hit the gas the fuel pressure would DROP like a rock. I took the inline out and everything was fine. That's about the time I ended up taking the whole kit off the car so I didn't worry about upgrading the fuel system anymore.

 

i changed the filter right before the install...when the key is in the on position, the pump is loud as hell so i know its on...but could it still be bad? i know its on because when i first wired it i thought it was on but that was just the stock pump putting fuel through it but now its LOUD...this sucks, i need to get this figured out My idle FP is aorund 48 or so and when i hit the gas it rises normally until it reaches58 then it either stays there if im at partial throttle but if i hit it, it drops fast...

 

okay GMC SKI what kinda FP do u see under boost? i changed up some wiring and my idle FP went up to 52, and now the FP rises with the throttle unitl about 62 under 4 or 5lbs of boost i didnt take it any further.... its paranoia city over here i had to conivince myself for about 15 mins that it would be okay to punch it really fast and let off to see if i see anything wrong with the FP.... but it doesnt climb too much after 62 but it doesnt drop any more though at all.... no more spiking in the FP it gets into bosst jumps to 62 and kinda sits there i wasnt loggin cuz i just took it down the block to see if that wire made a diffrence and it did but is that FP safe enough to boost under...???? thanks guys sorry for being so ignorant.. i apreciate all the help!!

 

At Idle mu Fp is at like 57-58 kinda hard to tell on the autometer guage
It rides to 62-65 depending on the boost
What's your injector flow rate number ?mines at 5.22 now with the fuel preasure that I'm at
That fuel Pumpe draw quite a bit of power so the wire has to be the right size
let me know how things are running with that

jim

 

my injector rate is at 5.00 and the truck finally drives normal... my FP tends to be around 52 but my idle is really low like 480RPM i dont like that.. yeah the fuel pump wire was it... i switched it up and things are looking better but im not sure if i am ready to start boosting quite yet... more tuning still left parish has been teaching me alot of sutff i had no idea about in the past few days...oh and my misfire is gone... oh yeah what gauge wire do you run directly to your fuel pump?

 

Ok here we go My Injectors rate is at 5.22
what I had to do with the Charger is bump up the idle just a tad to compensate for the load of the charger
Did you ever get Sams edit File ?
Did i send you mine ?
I would bump the FP a bit
if you were going to use my injector rate


jim

 

i have neither edit file, i would liek to look at your and his to see what you guys are doing...how should i bump up the FP? and idle?