Ok folks,I am back to the same old song and dance,i am determend to get to the bottom of this.I know someone here had to of have this problem.Let me qiuckly explain.
1.Powerdyne SC#6 pulley- #4/4.5 Boost
2.95 LPH Pump(stupid but no problems)w/12:1 FMU
3.#19 Injectors
Car ran great for 2 years......
4.Added #9 pulley,MAF Cal, #30 injectors and 255LPH pump(no FMU)#5 to #6 boost
Car ran like crap and didnt want to get a chip burned for injectors since stock heads and intake.Car ran so rich i was blowing black rich running smoke out the tailpipes at WOT.To much fuel,so decided since low boost to go back to stock injectors and MAF,kept 255LPH in.When i hooked the FMU the IDLE PSI was up to around 61 PSI,whoa too much.so i added a Kirbin AFPR,could not bring FP down,so i thought the FMU was shot,got a new Vortech FMU,same thing,tried a new FPR,nothing,same thing.Checked all lines for clogs,nope,checked for vacumme leaks,nope,checked FMU lines,ok there.Could not get the IDLE FP down no matter what i tried,so i put the 95LPH pump back in and,wow,the pressue went down to 40PSI.I was ok till now.I want to add an eldebrock intake and add more fuel so i decided to put in a 155LPH pump,OK same FP crap,up to 60 some IDLE FP.
It seems to me,even though i cant find anyone yet with this problem,that any Pump bigger than the 95LPH is causing my IDLE FP with the FMU to sky rocket.WHAT GIVES.Is the factory fuel rail to blame for all of this sh*@?Or is the lines off of the FMU to small?They seem to be what everyone else is using.
I have #24 injectors w/MAF i am using with the 155LPH pump and have a 8:1 disk,but untill i figure out the FP this will not be work,since i cant get the IDLE pressure down with the FMU.
Please help if possable.
Try a 6:1 disk in the fmu. No matter what combo you have, I would dyno-tune the car. Might be able to solve your fuel pressure problem right there as well. Your 94GT is not running to its full potential without some sort of tune.
__________________
There are only three things the copilot should ever say:
1. Nice landing, Sir.
2. I'll buy the first round.
3. I'll take the ugly one.
I almost bought a used Powerdyne from a guy back East. I talked to him on the phone about his whole setup and he had some similar experiences as you. I will PM you his e-mail address and perhaps he can tell you what he did to make his 9lb pulley work.
I do recall him saying that the fuel pumps are normally rated in volume and that they can vary on the pressure. When I bought my 255 lph pump they had a regular and high pressure version. I was very reluctant to even get the 255 because of this exact problem, but the tech where I got my charger was very insistent on me getting that pump in a normal (not high pressure) rating. I was gonna buy a 190 lph, so the profit differential for this guy was nothing and he was truly trying to help me out.
Isn't the fmu only supposed to restrict the return flow of gas under boost situations? If that is the case, then it should not come into play during idle. Perhaps there is more to it than that.
__________________
95 GT Convertible
BBK shorties, X-pipe, Magnaflow CB
CAI, 70mm TB, GT40 intake, 1.7 RR, UD pulleys
SFC/braces/JR, AUC Arms
1966 C Coupe - New restoration project
2004 Chev Silverado 4X4
Originally posted by GT Dan
Isn't the fmu only supposed to restrict the return flow of gas under boost situations? If that is the case, then it should not come into play during idle. Perhaps there is more to it than that.
You are right, at idle, it wouldn't matter what fmu he had. Forget what I said above I still recommend a dynotune with a custom chip though.
I guess the right question to ask here is of all of those with 255lph pumps in their tanks.....what kind of pressure are they getting at the fuel rails at idle???
If the only variable that is changed is the fuel pump....then a closer look at the pump and an inquiry as to what others are getting at the rails with the same kind of pump is in order. Once that is sorted out, then look at performance throughout the RPM range with the other variables.
Maybe he needs to move it to the 5.0 tech section and just focus on base fuel pump pressures?
I have the same system that I'm gonna install in just over a week so I'll be watching his posts for some heads up tips!!!
__________________
95 GT Convertible
BBK shorties, X-pipe, Magnaflow CB
CAI, 70mm TB, GT40 intake, 1.7 RR, UD pulleys
SFC/braces/JR, AUC Arms
1966 C Coupe - New restoration project
2004 Chev Silverado 4X4
I am going to check on this after i get my intake installed with the #24 injectors, but a guy on corral told me that with the high flow FP and stock injectors with the FMU caused this problem for him,he said with #24 injectors installed it will not put the resistence on the FMU return line that the #19 injectors do,so i will let you all know what i come up with.Sound right in theory so far.I will see.
Well,i put the intake on with the 24 Pound injectors and the pressure with the FMU is down to 50-55,now with the FMU on and calibrated with the 4:1 disk i figure this is taking me up to 75 PSI at full boost,Any suggestions,or is this safe for now?
Now the thing i noticed,if any suggestions is that when i started the car up it seem the timing was all messed up but when i disconnected the EGR valve the car idles great,is the valve shot or is it something else,any help?
FMU & 155LPH Pump=2 much FP 
I still recommend a dynotune with a custom chip though.
