OK, I tried setting the fuel pressure with the new afpr with motor running, vac hose to afpr disconnected and PLugged, by the way it did not seem to make any difference if it was plugged or open. With vac line off had about 52 psi, with on about 42psi. Backed out screw on afpr trying to get down to about 45, went down to 50 psi with vac line off, began to suck air through screw hole, in other words screw was almost all the way out.
So WTF!. I can only get the pressure down to 50 psi with vac line off and 40 psi with it on. Why is that? 50 is probably to much, I bought the afpr used, maybe its no good.
thanks

 

What kind of AFPR are you using?

 

I am using a BBK AFPR and I could not get my fuel pressure below 41 PSI (stock fuel pump). I am running #30 injectors so I wanted to get around 37-39 PSI. I was told that you should be able to drop the pressure to the mid to low 30's. So I am also wondering why I could not lower the fuel pressure further?

 

It is supposedly an Accel AFPR that I bought used from a guy on this website. It consists of a aluminum cover, with a threaded hole and a bolt in it, and a flat round metal piece that goes inside. When you screw in the bolt it pushes the flat round metal piece down onto the spring loaded diaphragm deal and changes the fuel pressure. I guess what Im saying is that with the bolt all the way screwed out, to the point that it sucks air through the bolt hole, the fuel pressure only goes down to 50psi with the vac hose off.

 

Yeah, thats sounds like mine. I put an Accel on and couldn't get it below 50.5psi. Then I made the mistake of using SVO 24# injectors, not knowing that they rate theirs at 39.5psi. That made it about 27.2#. Horribly rich!

The diaphram just needs to strech, within time my psi came down a little bit. I don't know a faster way, maybe someone else can chime in.

 

The only thing that I can think of is replacing the steel plate insinde, the one that pushes on the diaphram spring, with a thinner one. Other than that I don't know.

 

That plate is pretty thin to begin with. Im not getting much change in pressure when I turn the screw. I had it about 1/2 way in and screwed it all the way out, and it went from like 52psi to 50 psi only. Does that seem right. Im thinking about jerking this sucker off and putting the stock one back on. I changed it and added an Accel base and gots slightly worse performance. Im thinking the fuel pressure was too high and its running rich.

 

Yeah something is not right! I guess I would just go back to the stock one in your case. You probably have lack of performance because your pressure is so high.

 

Has anyone had any luck reducing fuel pressure using the described AFPR? If so, what is the lowest presure achieved? Do the size of injectors make a difference?
Larry, I hope you don't mind me chiming in on your thread, but you asked the exact question that I had.

 

sounds like something is wrong with it... try pulling it a part and see if the diaphram is messed up... that same thing happened with my buddies iroc... we tried to lower the pressure and it wouldn't go down... ended up his TPIS AFPR had crapped out on him... so it wasn't getttin a real reading anyways...

 

if you have to get a new afpr get the holley. it has a diff., yet better design. approx. $80

 

What about the diafragm though? I had never laid eyes on one before I opened up the stock FPR and put this new one on. What do I look for to tell if its messed up? If I cant get this one to work maybe I;ll go with the Holley. Kind of an expensive lesson on AFPR though. Thought I was getting a deal.

 

my buddies was all freaked up... it was turned at a 45* angle in the bottom in stead of being flat across... it was giving freaked up #s cause of it...