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-   -   Fuel Pressure Regulator hiss (https://www.zdriver.com/forums/300zx-z31-forums-8/fuel-pressure-regulator-hiss-43969/)

Hefferd Sep 20, 2025 01:51 PM

Fuel Pressure Regulator hiss
 
I am having trouble with my Z staying on. It runs, then sputters, then dies.

I am convinced it is plumbing related. Here is what I have unanswered so far:
  • Fuel pump on Acc. does not stop humming, sometimes even slightly changes pitches. It hums for as long as I stay in Acc.
  • Fuel Pressure Regulator makes a hissing noise (almost like when you turn on a sink), but there is no sign of a leak anywhere.
  • Sparkplugs have nice white coating on the node (lean).
  • Fuel filter is brand new.
  • Fuel pressure test kit yielded zero psi on crank and during the 3 seconds it stays on. This makes me think that perhaps it only stays on and uses the fuel that was initially primed into the lines.
Here is what I want to know:
  1. What is going on? (that is a given)
  2. Should my fuel pump stay on for that long in Acc.?
  3. How do I test if my fuel pump has a good ground?
  4. Could my FPR be bad but not show symptoms like fuel leak etc?


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