AFPR -- vacuum line?? And fuel pressure adjustment question

jb89coupe

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Sep 3, 2004
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Ever since putting my crane AFPR on my car it's been giving me problems in the lower rpm's (hesitation, missing). I'm pretty sure the real problem is my TFI module (going to replace that soon), but I've been searching through threads on fuel pressure adjustment and I've noticed everyone refering to vacuum lines on their aftermarket regulators.. my crane doesn't have one, just a set screw. Could the lack of vacuum to the regulator be negatively affecting my fuel pressure?

Also, any advice on how to optimally set my pressure? Just bump it a little bit and drive around? Do I need to reset the computer every time? With lower pressure the car has no power and breaks up bad down low but runs great after 2500rpm or so.. with higher pressure it picks up a little down low but doesn't pull as hard up top, and it shoots rich codes. o2 sensors are brand new, this happens with both of my mas's (both worked fine before the heads/intake).. Any thoughts as to why I'm leaning out in the lower rpms?
 
Yes, no vacuum to increase fuel pressure to the injectors will certainly affect how the car performs. To set pressure, disconnect the vacuum line, plug it, install your pressure gauge on the schrader valve, start the car, and start adjusting the set screw/nut on the regulator. With your combo, I'd suggest @45-48 with the vacuum off.
 
Sorry, I'm a moron. I just dug up a manual for the regulator online, and apparently the adjustment screw IS the vacuum line (there's a small hole in the head of the screw, duh).. :doh:

I just hooked a line up from the regulator to the upper manifold and took it for a spin. It hasn't solved my low rpm hesitation. My fp is at 46 with vacuum off. You can feel it start to pull down low, but then it just backs down and stutters. Once is hits 2500 it's like a switch turns on and it takes off. I'm going to replace my TFI and PIP before I go crazy thinking it's a fuel issue, but has anyone experienced something like this before?
 
jb89coupe said:
Sorry, I'm a moron. I just dug up a manual for the regulator online, and apparently the adjustment screw IS the vacuum line (there's a small hole in the head of the screw, duh).. :doh:

I just hooked a line up from the regulator to the upper manifold and took it for a spin. It hasn't solved my low rpm hesitation. My fp is at 46 with vacuum off. You can feel it start to pull down low, but then it just backs down and stutters. Once is hits 2500 it's like a switch turns on and it takes off. I'm going to replace my TFI and PIP before I go crazy thinking it's a fuel issue, but has anyone experienced something like this before?
Yeah i had a similar problem and it was the TFI module