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Fuel Pressure - 60PSI all the time

596 Views 9 Replies 2 Participants Last post by  JohnHZ31
Working through our new '85 2+2 NA and the last major issue is that the fuel pump is running ALL the time and it's giving 60PSI at the rail, which we know is too high for NA.

1. The PO joined the two ground wires in the fuel pump connector. That's obviously why it's running all the time (ign on).
2. When we correct the wiring the pump primes for 5 seconds then stops. It does not turn back on during crank AND there is no spark during crank! When I go back to the hacked wiring I get spark and fuel (but at 60PSI, which I'm afraid is going to damage the stock injectors).
3. ECU Pin 108 is grounded for 5 seconds after ignition on then no ground after 5 seconds. Does not come back during crank.
4. ECU Pin 20 is grounded for 5 seconds after ignition on then no ground after 5 seconds. Does not come back during crank.
5. FPR is GOOD. FPR can't reduce pressure anyway because it's downstream from the rail. It only regulates at a particular pressure.
6. I haven't tested with another ECU but I'm starting to think that has to be the source of the problem.

I'm stumped so ANY suggestions would really be appreciated!
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How do you know the FPR is good? what's the point of a FPR if it can't reduce pressure?
I've tried three different FPRs and the result is the same every time. How can any unit that is downstream from the rail reduce pressure on the rail? The pressure can never be less than what the pump is pushing out, all it can do is close down a little to increase pressure and regulate it. Once the FPR is WIDE OPEN it can'y reduce pressure any more, right? Removed the FPR completely and I still have 60PSI on the gauge before the rail. I think the main issue is that the fuel pump is running at 100% voltage all the time - wide open all the time (with the hacked wiring).
z's do not adjust fuel pump voltage to adjust fuel pressure, your wiring sounds right. The regulator still works downstream. It's supposed to relieve excess pressure into the return line to leave the correct pressure in the fuel rail. Picture a tank of compressed air, you spray air out of the hose and it lowers the pressure in the tank until eventually there is none left. Same idea applies with the fuel pressure, so I would think you need a new FPR
Understood, Mydoor. What if my pressure is 60PSI at the gauge with NO regulator (I removed it completely to test). I’ve checked the return and it’s not blocked. FSM says voltage is reduced / increased by the ECM depending on temperature and conditions.
If the FSM says it then it must be true. It's supposed to run at about 40-ish PSI with no vacuum at the FPR, I tested my FPR by plugging the vacuum line that goes to it, and connecting a handheld vacuum pump to the FPR. Then run the fuel pump and see if the pressure lowers as you add vacuum, like I said it should be at about 40psi at 0 vacuum. The FSM should have a table of the correct vacuum-to-psi ratios you can test to tell you if the regulator is working
Even with the FPR completely removed (running with the return line unhindered) I'm sitting at 60. So d**m frustrating! I've tested the return line in the engine bay and I've blown through the return all the way to the rear and didn't "feel" any blockages but I think I'm going to recheck that one last time. Car runs smooth, just really rich.
My fpr failed and my car was running at about 60 psi too, when I pulled the return line off the FPR and no fuel was coming out when I powered the fuel pump. Replaced with the 75-77 280z fuel pressure regulator and now my car doesn't run rich.
It’s so weird. I’ve tested 3 different FPRs and checked that fuel is coming out of the return line. Return line is open. I even ran it with no FPR, still 60.
Has anyone here replaced the whole return line? I'm assuming I can just do it with injector hose rather than trying to find the hard lines somewhere.
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