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Fuel pressure questions, startup.

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  • Fuel pressure questions, startup.

    Well trying to track down some hard start issues, I am pretty sure that it is a fuel pressure, or lack thereof, issue. The fuel pressure is dropping to 0 after sitting for a bit, and when I turn the key to the on position I hear the pump prime but the fuel pressure only spikes for a second and then drops back to 0. What is the guess, leaky injector (how to check), bleeding FPR, or bad pump?

  • #2
    I had the same basic issue on my S13. You may want to check the rubber hose between the pump and the hard line. If there is no fuel leaking anywhere under the vehicle etc., it may just be a tear or something in the hose, causing the fuel to circulate directly back into the tank!

    This happened to me a few years after i installed a Walbro 255. Apparently the hose they give you with the Walbro kit is garbage. Replaced with good hose and no more issues!

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    • #3
      It's easy to check by pinching the rubber hoses with pliers. You can prime the pump with the return hose pinched to see if the FPR is bleeding down, then pinch the supply hose immediately after a prime to see if the check valve in the fuel pump is bad or somewhere in that feed line. If you are still bleeding down it could be injectors. You may also want to check the vacuum hose on the FPR for the presence of fuel indicating a ruptured diaphragm (pretty unlikely on a Nissan).
      98 240SX SCCA STUish

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      • #4
        Originally posted by Joe D View Post
        It's easy to check by pinching the rubber hoses with pliers. You can prime the pump with the return hose pinched to see if the FPR is bleeding down, then pinch the supply hose immediately after a prime to see if the check valve in the fuel pump is bad or somewhere in that feed line. If you are still bleeding down it could be injectors. You may also want to check the vacuum hose on the FPR for the presence of fuel indicating a ruptured diaphragm (pretty unlikely on a Nissan).
        This man knows what he's talking about. In other words, you might have a bad FPR or a leaky injector.

        If it's a bad FPR alot of times when you take off the vacuum hose fuel will leak out. Also as he said just clamp the line that returns from the FRP and see if the cars starts up easier. With that line pinched off and you still have problems and don't see gas in the vacuum line then I'd start thinking about a leaky injector, but it would have to be leaking really bad from what it sounds like.

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        • #5
          Leak somewhere in the system, or the check valve for the fuel pump is dead.

          Pull the rail and see if an injector is leaking. I'd imagine a fuel hose leak would be VERY obvious due to the smell. If those check out, I bet your fuel pump has a dead check valve.

          Jump the pump to keep running while you crank and I bet it'll start up if the check valve is the issue.
          '18 Chevrolet Volt - Electric fun hatch for DD duty!


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