NC280z Posted September 27, 2014 Report Share Posted September 27, 2014 Hi all, Just want to get clarification on testing the fuel pressure regulator on my '75 280z. I'm getting around 24psi fuel pressure at idle, and it's keeping me from driving anywhere. When I remove the vacuum line on the FPR, the fuel pressure jumps to the factory rating of 36psi, and the engine runs like a champ. FSM states that if 36psi isn't seen at idle, replace the FPR, and then replace the fuel pump if all else fails. Can't find anything in the FSM or fuel injection bible on if disconnecting the vacuum line and seeing 36psi means the FPR is good or not. Is the FPR my issue, or should I check other components? Quote Link to comment
datzenmike Posted September 27, 2014 Report Share Posted September 27, 2014 Your pump should be capable of about 40 to 60 PSI without regulator. I guess if you pinch off the return line from the regulator to the pump it should read full pressure. If not... why not? maybe the pump isn't capable of it. Idle fuel pressure should be low 30s and jump to about 37 than throttled. Quote Link to comment
NC280z Posted September 28, 2014 Author Report Share Posted September 28, 2014 I should also note that my manifold vacuum while running was around 15". The fuel pump it has currently is a Delphi FD0035, and the fuel filter and all fuel lines are new. *EDIT* I tried pinching the fuel return hose today, and no increase in fuel pressure. Fuel pump issue, maybe? Quote Link to comment
HRH Posted September 29, 2014 Report Share Posted September 29, 2014 Your regulator is bad I would say. Install an adjustable fpr like I did on my 240 Maxima. $35 offline, el cheapo, but works great! Quote Link to comment
NC280z Posted September 29, 2014 Author Report Share Posted September 29, 2014 So I've swapped the fuel pressure regulator and fuel pump, and the car runs great. Fuel pressure still stays at 30-28psi at idle, but goes up to 36 under load. From what I've read, the FPR is supposed to keep the fuel pressure differential at the equivalent of 36psi, so 18-20inHG vacuum=6-8psi, 36psi fuel pressure minus 6 or 8psi vacuum= 30psi idle fuel pressure. Am I correct in this? Quote Link to comment
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