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Fuel pressure pulsating at idle?

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  • Fuel pressure pulsating at idle?

    Just curious if you guys have experienced this? Maybe its my gauge or something else. I had a matco fuel pressure gauge on my lines the other day and with the fuel pump at full voltage the gauge was bouncing quite a bit. Anyone notice anything similar?

  • #2
    Is the gauge internally damped, or the oil-filled variety? A small pressure fluctuation is normal if it's just a couple PSI with the car at idle.

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    • #3
      Is the car vacuum steady?
      Try not to be a Yahoo

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      • #4
        I doubt the gauge is damped. It's not that I think anything is wrong I just thought it was interesting.

        Vac is steady.

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        • #5
          Mine used to do that. I had an autometer POS fuel gauge. I don't really know mine doesn't pulse that much anymore since I moved my regulator closer to the fuel rail. I also I have replaced most of my soft fuel lines with hard tubes to minimize the amount of ballooning in the system.





          tbs
          Blue & Silver 81 zxt, 88 ECCS
          Z32 mas,450cc injectors
          ported exhaust manifold, cable throttle linkage
          t3/t4e 12psi , 3inch exhaust, K&N,
          ACT clutch, 240sx t/b, 1G DSM BOV
          Custom Intake FINISHED
          Ported and Polished N42
          Tan 88-89 conquest seats
          Sperco IC 18.5x6x3.5
          2.5 IC pipes
          Suspension work!!
          Nistune
          Zeitronix Wideband
          240sx transmission
          Soon:
          95 Maxima Alternator

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          • #6
            Do we dare place bets on the Culprit being the fuel hose(s)?
            (why is it when we are flat broke that we dare to place bets?..heh)
            *My 86t.....I had an autometer electrical FP guage, new hoses, stock FPR, Z32 TT pump, stock injectors and rails....no pressure fluctuations.
            8)
            :idea:
            *I suppose I shouldn't assume. You are describing a fluctation while idling..correct?(where the pressure/demand on the pump is at a minimum) It would interesting to see what happens when you are under load on your dyno as the pressure increases. It might be as simple as a design characteristic with the pump.(pressure relief bypass)
            (Low volume/low load...high pressure pump)
            I am here to help...

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            • #7
              Old fuel hoses would probably damp out those fluctuations more than accenting them... But I doubt it would be a notable amount either way.

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              • #8
                mine was new aftermarket hose from autozone. I think goodyear and you can see as pressure rises the line ballons one day I cranked the pressure up and it got at least I 1/3 larger in diameter. Its some stupid crap that its fuel injection line and that it can handel the high pressure yah its supper stretchy. Don't worry I've broke this crap twice before switching to hard lines. but all my stock nissan lines are prefect.



                tbs
                Blue & Silver 81 zxt, 88 ECCS
                Z32 mas,450cc injectors
                ported exhaust manifold, cable throttle linkage
                t3/t4e 12psi , 3inch exhaust, K&N,
                ACT clutch, 240sx t/b, 1G DSM BOV
                Custom Intake FINISHED
                Ported and Polished N42
                Tan 88-89 conquest seats
                Sperco IC 18.5x6x3.5
                2.5 IC pipes
                Suspension work!!
                Nistune
                Zeitronix Wideband
                240sx transmission
                Soon:
                95 Maxima Alternator

                Comment


                • #9
                  part stores always want to sell you "fuel hose" that is for carburated and not injected vehicles.... it's such a scam, what's the point, every car is injected

                  anyway go to a hydraulics shop and pick up the right size and classification hose, just tell them you need at least 50psi and they'll say "oh you want low pressure" and pull some out for you

                  all the hoses I picked up are 300psi except the 2500psi double shielded nylon braided abrasion resistant stuff from the hardline to the filter and filter to fuel rail.... reason being I needed something that wouldn't crush when you bent it and wouldn't chaffe running along the body metal

                  everything I bought was

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                  • #10
                    If a non liquid filled gauge is used on the feed side fuel rail you will most likely experience this.

                    It happens on alot of cars. especially if the FP gauge is connected before the rail.
                    Gone - 1988 Shiro
                    2004 BMW 330Ci
                    2005 BMW 330i
                    1991 Twin Turbo Z's (Red and Black)
                    http://www.E46Turbo330Ci.com

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                    • #11
                      fuel pulsations and fix

                      I was getting about 3-4 psi of pulsations, just about everywhere. This did bother me quite a bit as it made tuning harder, and I was not getting the resolution I wanted in the tune.
                      I found a damper that fixed all of my problems. The unit was 135.00 shipped to me and it WORKS!
                      http://www.injector.com/fueldampers.php ... 49aeea4875
                      check it out, well worth the money.

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