fuel pressure..

[larryd]

im pretty sure its the spring the came with it..

there is vacuum on the line that goes to the FPR

the line doent appear to be damaged from what i can see, its Td off to the boost gauge I know that much and the boost gauge works fine or so I think.

I let the car sit there and idle for like 5 minutes and it still shows 43 with the line on and off.. Ive checked it several times now as well and I get the same thing.

 

[HighPsi91]

I am pretty sure Steve hit the nail on the head. I have heard of several people having trouble lately with these regulators. The spring probably needs to be changed to a stiffer one.

 

[larryd]

ugh.. whats with all these parts on my car giving out on me.. where do i get a stiffer spring?

 

[steve]

Maybe, I went out to the garage to get the little sheet of paper that came with mine. It says the stock spring is good from 35-55 psi and the heavy spring is for 45-65psi but who know how accurate the paper is. The proof would be in how far Larry has to adjust the screw to reach 43 psi with the hose off. I know I have to tighten it a bit to get 37 as a base on my 1g and it seems like I've had to tighten in reciently to keep it there. It's possible with all the changes they made getting the various versions out that the springs are different from what they wrote up. If you have the torx screwdriver to fit the fasteners I'd try switching the springs. It came in the box with the allen bolts to attach the AFPR.

Steve

 

[HighPsi91]

Actually I think they come with a stiffer spring. Its either in your box of parts or mine. At the time I had no idea what it was for

In fact I remember having to screw the adjustment screw in quite a bit just to get near 40psi. I thought that was kind of odd at the time. I dont recall ever seeing an instruction sheet however.

 

[steve]

Yea, having a 1G I looked at it and said, what am I going to need this for!
It's still in the ziplock bag in the box at my feet.

Steve

 

[larryd]

hmm. when I was adjusting it yday I didnt have to much of a problem.. in otherwords it didnt seem like it was all that tight to me.. Wes can you check your box and see if you have that spring.. Ill check mine but I dont recall see'ing a spring.

 

[jdmawd]

Originally posted by larryd
ugh.. whats with all these parts on my car giving out on me.. where do i get a stiffer spring?

if you have the charged air FPR, it should have come with 2 springs

 

[jw]

Yeah, it comes with 2 spring. The spring that is in the FPR is the lower pressure spring. I have around 1/2" thread left when I set it to 37psi. The stiffer spring is for above 60psi.

If you dont see a difference with the hose in and out, you should call them.

 

[larryd]

Well I figured something out regarding the fpr tonight. When I turn
base pressure down to 40psi with the hose off and I put the hose
back on it drops to 30psi. When I set it at 41psi+ with the hose
off it stays at 41+ with the hose on. I have no clue why but I
turned it down to 40 until I can figure this out.. anyone have any
idea??

I also did a boost leak test and Ill be damned if I wasnt right. I
have a MAJOR boost leak between the intake manifold and the head
(lucky me). I pressurized the system and once it hits 7lbs of boost
it wont go any higher and you can hear the air coming out rampant.
I got a spray bottle and sprayed it on the area it was coming from
and air is seeping out between the intake manifold and the head. So
now I get to pull the IM back off the car and put a new gasket on
it..

 

[steve]

Originally posted by larryd
Well I figured something out regarding the fpr tonight. When I turn
base pressure down to 40psi with the hose off and I put the hose
back on it drops to 30psi. When I set it at 41psi+ with the hose
off it stays at 41+ with the hose on. I have no clue why but I
turned it down to 40 until I can figure this out.. anyone have any
idea??

Sounds like it's time to find your other spring. The only reason I can think of is mechanical binding when you increase the compression on the standard spring to get past 40 psi.

Steve

 

[larryd]

thats what im thinking as well.. now i just need to find it

 

[NJGSX96]

Originally posted by larryd


I also did a boost leak test and Ill be damned if I wasnt right. I
have a MAJOR boost leak between the intake manifold and the head
(lucky me). I pressurized the system and once it hits 7lbs of boost
it wont go any higher and you can hear the air coming out rampant.
I got a spray bottle and sprayed it on the area it was coming from
and air is seeping out between the intake manifold and the head. So
now I get to pull the IM back off the car and put a new gasket on
it..

Wow that sucks. Are you sure all the bolts were tight? Long shot probably but worth checking.

 

[larryd]

yeah.. i checked em all last night and those suckers wouldnt budge.

 

[Rodman]

Your boost leak is giving you all your problems. My BFP is at 44 psi and 39 with the hose on. I have a heathy vac of ~20, so a drop of 10psi seems weird. What is your vac at idle?

 

[larryd]

hmm.. well my boost gauge is in bar.. but at idle its around 500.. not sure what the reasing is actually of though.. like cm/sq or something like that.

 

[steve]

Conversion Factors

1 bar = 14.5 psi = 29.53 in hg = 1.02 kgf/cm2 = 750.1 mm hg
20 in hg = 9.823 psi
500 mm hg = 19.69 in hg = 9.668 psi
1 in hg = 0.4912 psi = 0.03386 bar = 25.4 mm hg
1 psi = 0.06895 bar = 0.07031 kgf/cm2 = 2.036 in hg = 27.68 in h2o = 51.72 mm hg

It look like the metric boost/vac gauges read mm hg (or cm hg) on vac side and kgf/cm2 for boost where US versions read in in hg vac and psi boost.

That's why the fuel pressure drop should be about 10 psi, hose on compared to hose off assuming you have normal engine vaccum. You forgot to convert units.

Steve

 

[larryd]

ok so since its reading at 10 vacuum thats why i lose 10lbs of pressure when I pull the line.. that makes sense actually.

 

[steve]

The idea is that the FPR track manifold pressure 1:1 so that the same amount of fuel per unit time comes out of the injectors. So at idle vaccum the fuel pressure is reduced by the difference (10psi less than base) and as boost builds the FPR raises the pressure so at 1 bar boost the pressure is 14.5 psi over base. For those that don't quite follow it's the difference between inlet pressure and outlet pressure that controls flow rate for a given oriface. It makes it easier to calculate the amount of fuel per unit time if it stays consistant and keeps the injector output from tapering off as boost pressure rises so you don't need even bigger injectors.

Steve

 

[larryd]

then how come when i go over 40psi as a base with the hose off when i put the hose back on it stays right at 40psi?? If I keep it under 40psi base then it drops 10psi with the hose on?

 

[steve]

Larry, I know your having a lot of problem with your car right now but I've given you my best answer twice already. I think your spring in the AFPR is binding when you set your AFPR over 40 psi base. Applying vacuum to AFPR will try and work against the spring and compress it more. If it's already maxed out then the vacuum trying to pull the diaphram back a bit isn't going to happen and your pressure won't drop. If the spring is that compressed you might have problems on boost side too. Springs work best in the middle of their range.

That's my best guess. I'm hopeful this problem turns out to be that simple and that you haven't bent the diaphram.

Steve

 

[larryd]

well that makes sense.. i understood the spring to be the problem. I just didnt understand why.

 

[umiami80]

Does teh car drive a lot better with this thing on? How is it driving around town? Way better?

 

[larryd]

i dont know, i havent got the spring yet.

 

[steve]

Larry, did you solve the problem?

Steve