Fuel pressure "issues"

[leirch]

Guys,

Here is the deal.

I have an 87Iroc-z camaro. I just did a 3.8/200r4 conversion. I did the wiring myself(yes, it was fun but wasn't too bad really).

The car fires right up, hold 43lbs fp at idle line ON. But when I get on it, my boost guage reports about 16psi and sometimes tries to climb higher(I left off of course).

The engine is a 70k mile motor, stock injectors, stock cam(new, old one had the classic #3 exhaust lobe gone), ported intake, and a 9inch K&N filter.

The turbo is stock, no shaft play and a stock waste gate, stock GN downpipe.


Now that you know about the car, here is the deal, the fuel pressure will go up to 60lbs if I feather the throttle but If I all out floor it the boost shoots up to about 16+psi on my mechanical autometer guage(I'm a little leary that this is under reported, since I can hear the car spooling and pulling before boost registers on the guage).

I have replaced the fuel pump recently(2 days ago) and put a new fuel filter on.

I have also done a homemade hotwire setup to the fuel pump(10guage power wire with a 30a relay).

I have switched vacumm ports from the FPR to various intake ports and that hasn't changed anything(figured, may it wasn't getting proper vacumm?). I do have an adjustable FPR also(have tried a stock one as well, same problems).

Now, the car does have vacumm brakes, I have simply ran the vacumm line over to a port on the intake for that, brakes seem to work fine.


The weird thing is, "sometimes" the fuel pressure will ride high and work as intended(60+ psi). It even did this before I did the hot wire setup.


I've come to the conclusion that there may be something in one of the fuel lines? Like a piece of rubber or something like that.. I don't know though.


Any ideas/help would be appriciated though.



Thanks,
Brendan

 

[leirch]

I forgot to mention, the FP is a Walbro 340.

 

[scottyb]

I don't understand what the problem is. The stuff stated in your post appears to be correct.

 

[Slow91z]

Ok I'm confused...Did you ask a question in that entire post?? Is your question about fuel like the title suggests, or are you asking about boost?? They are separate issues.

Oh and 43 pounds of FP with the line ON is a bit much for a stocker...You should set the FP with the line OFF.

 

[xxninja]

your issue doesnt sound too bad
i had a similiar problem.

after tinkering with it for like 2 weeks, some1 suggested borrowing a friends fuel guage

turns out it was just my guage.
see if u can borrow 1 from a friend,
see if its more consitant.

also........

youy didnt specify if you went with 84-85 motor or the 86-87
but since this is the hot air forum, i am assuming you went with our engine...


make sure you dont have any leaks in your rubber hoses that connect the fuel pressure regulator to the back of the intake.

specifically the rubber hose that goes on top of the FP regulator
to the steel line .....

and then at the end of that steel line, it curves and then there will be another rubber hose that connects to the nipple on the back of the intake.
make sure that rubber hose is tight and in new condition


if you dont know what i mean, check out the Sticky Forum at the top. and look at the vacuum diagrams

 

[leirch]

My problems are that the Fuel pressure is falling off when I'm in Boost.

This is a 86-87 setup. I will try setting the fuel pressure back down.

Say I'm at 15lbs of boost, the fuel pressure will only be at 50psi.

The strange thing is, randomly, the fuel pressure will go above 60+psi when at the full 15lbs of boost.

 

[87GN_70GS]

This test might tell you something: With the engine idling (or engine off but power applied to the pump connector), apply varying levels of air pressure to the regulator, i.e. atmospheric, +5psi, +10 psi, +15 psi, etc. See that fuel pressure tracks with the base setting plus the "boost" you're applying. Try different base pressures. This may or may not discover the problem.