I was recently able to track a rich condition down to my Holley AFPR. It seems that it does not drop pressure at all when there is little to no vaccum. It stays at constant pressure. But before we say the AFPR is bad I will say that I see manifold idle vaccum in the low 50s as I have an LT4 "hot" cam. So needless to say I have less vaccum than stock cars.
I am able to start the car, rev the engine, disconnect the vacum line and repeat with the line disconnected and not have varying fuel pressure. I do get varying MAP readings from 30-100 so I am deffinatly seeing fluctuating MAP for the AFPR to dhange. Also the line is not bent or anything. The pump can handle the fuel pressure as it is a new walbro and does not drop pressure at higher pressures at WOT.

I guess what I am wondering is is my AFPR diaphram bad or is this expected. I have heard about Holley AFPRs having trouble in the past.

 

If the vacuum doesn't change fuel pressure, decrease it, then I would say AFPR isn't working as well.

 

My holley AFPR that comes with the HSR doesn't have a vacuum port IIRC...

 

Interresting, how does it regulate fuel pressure then? At idle you need less fuel/pressure, as engine vacuum decreases with acceleration you need more fuel/pressure. What is going to control that if your vacuum isn't?

 

TBI FPR's don't have vacuum control either. Although in the TBI you might have 12-13psi vs 43 with the TPI.

 

It has the vaccuum port inside the screw(down the middle of it) that is where a vac. line hooks up. If not, it is not an AFPR.

 

Tibo quote:
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Originally posted by iansane
My holley AFPR that comes with the HSR doesn't have a vacuum port IIRC...
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It has the vaccuum port inside the screw(down the middle of it) that is where a vac. line hooks up. If not, it is not an AFPR.


Thanks for clearing that up Tibo, I was thinking they came out with a MAFPR (magic automatic fuel pressure regulator) or something when I wasn't lookin.

 

Shrugging aside Bobsroc's last comment; I did some research of the Holley AFPRs and found that many times the wrong AFPR was sent out. Mine displays the same symptoms as others (10psi drop when turning the screw, not much idle/WOT difference).

 

Forgot to add that I found it out at http://www.stealthram.com (not to promote another website or anything.)

 

Sh*tty...So where am I supposed to hook that up now? Just any vacuum port off the manifold?

And is tightening that screw or loosening it raising FP?

 

bttt...? where's the vacuum line supposed to hook up to?

 

Normally it's hooked up to the plenum (not the throttle body)

 

Would it be okay if I T'd into the MAP sensor line?

 

Should be okay there.