studioti Posted April 12, 2011 Share Posted April 12, 2011 Car: 77 280z stock EFI except for pallnet style fuel rail Status: is running and have run steadily for the 4 years i've owned it. Problem: it drives fine, but i finally installed a pallnet style fuel rail with gauge on it and the pressure reads 25psi at idle and rises to 32-34psi when throttle is applied. Also, if i remove the vacuum line to the FPR the pressure on the gauge goes up to 35PSI and stays there no matter idle or on throttle. Comments: to be honest, the car runs and feels fine. i've just never monitored the fuel pressure until i bought the new fuel rail. i guess ignorance could be bliss...but now i know and it bothers me. haha Parts: • FPR 6 months old. Stock type but autozone brand • Injectors are 3 years old. stock type but autozone brand • Fuel filter 6 months old • All new fuel hoses in engine bay • Hard lines stock • Fuel pump same old stock one • Tank same old stock one Any advice is much appreciated. My thoughts are: • Upgrade to an adjustable fuel pressure regulator • Buy a new fuel pump • Install inline, clear fuel filter so i can see if there is any crud coming from tank or lines Thanks once again. Quote Link to comment Share on other sites More sharing options...
Administrators RTz Posted April 12, 2011 Administrators Share Posted April 12, 2011 It's supposed to be lower with the vac. line connected. The purpose of vac. reference is to maintain RELATIVE fuel pressure. Abridged edition: If your manifold generated 5 PSI of vacuum, then you would need 5 PSI less fuel pressure to maintain the same relative fuel pressure, yes? Quote Link to comment Share on other sites More sharing options...
studioti Posted April 12, 2011 Author Share Posted April 12, 2011 It's supposed to be lower with the vac. line connected. The purpose of vac. reference is to maintain RELATIVE fuel pressure. Abridged edition: If your manifold generated 5 PSI of vacuum, then you would need 5 PSI less fuel pressure to maintain the same relative fuel pressure, yes? Thank you. This does make sense to me, since you explain it that way. But do you think 25psi at idle and 30-32 on throttle is low? Quote Link to comment Share on other sites More sharing options...
Administrators RTz Posted April 12, 2011 Administrators Share Posted April 12, 2011 25 PSI is reasonable at idle, assuming a stock engine (camshafts and tuning will influence manifold vacuum which will influence a fuel pressure regulator). Fuel pressure should be 36ish at WOT, which is close to what you said in your first post. Quote Link to comment Share on other sites More sharing options...
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