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  1. #1

    Unhappy Fuel Pressure Issue

    Hi, all,

    I'm having a hell of a time getting this fuel pressure problem diagnosed. 2011 RXT 260 with a lot of parts. Full engine build by EastSide Powersports (9.5:1 CP Pistons, lightweight connecting rods, stage 3 cam, race ported head, ARP head studs, lightweight crank, double spring kit and retainers), Riva thru-hull exhaust, TDR Waterbox, Riva RRFPR, Bosch VT1100cc injectors, Riva fuel rail, Riva High Volume Fuel Pump, 4" Kanaflex Intake, intake manifold spacer and brace, Fizzle F1000 intercooler, 137mm supercharger impeller, JP Racing 9200rpm tune on 93 octane.

    At idle I'm seeing the fuel pressure fluctuate between 30-50 psi so it runs rough at idle. Also doesn't reach 9200rpm on the water (maybe 8200 if I'm lucky). Used to run 80+ mph well at 58psi and when I insert the key and briefly press the start button, fuel pressure does rise up to about 58psi. It just doesn't stay there.

    Pulled the rrfpr and it looked pretty clean. Pulled the whole fuel pump mechanism out and all I can find is a (slightly) dirty fuel filter. AFR gauge isn't working for some reason.

    Anything I should check? Anything I should replace? I'm about ready to sell this thing.

    Thanks for all your help!!


  2. #2
    raiderx72's Avatar
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    What kind of guage you running?

  3. #3
    www.eastcoastpwc.net Scott's Avatar
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    When you pulled the pump, did you double check the feed line wasn't split?

  4. #4
    SplishSplash's Avatar
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    He posted the exact issue in paragraph 2, Fuel pressure rises to 58 but does not stay there. Thats the issue to fix. Not a fuel tank or feed line issue.
    I assume you mean when you put the key on, it goes to 58 psi (not running) and does not stay there. You have to find where the fuel is going.
    Most likley a leaky injector or bad RRFPR. (look at spark plugs see if one is all wet or different from the others)

    If its working properly, putting the key on the post, its should prime to 58 psi, then even if you remove the key, it should hold 58 psi for quite a while( at least 1/2 an hr) , if not, thats the issue

    If it does hold, then look for fuel supply issues like mentioned in the above posts.

  5. #5
    Bob 1tommygunner1927's Avatar
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    Scott is correct in suggesting the in tank fuel line may be cracked or have a split at or near an attachment point. I experienced this exact issue a while back and it was due to making the fuel line too short thus creating a kink in the fuel line at the fuel pump when the fuel pump assembly was installed in the tank. In time the fuel line slit at the oetiker clamp. Key on showed 58 psi pressure and dropping very quickly to 10 psi with key off.
    Last edited by 1tommygunner1927; 09-30-2019 at 01:31 PM.

  6. #6
    Quote Originally Posted by raiderx72 View Post
    What kind of guage you running?
    @raideerx72, the rrfpr is Riva. Plugs looked pretty bad after about an hour of run time - I think it's running rich. How can it run rich on low fuel pressure, though?

  7. #7
    @scott, I did not check the line. I will do so tonight.

  8. #8
    @splishsplash and @1tommygunner1927 - I see exactly what you guys are saying. The pump primes up to about 58, but immediately drops back down to 0 if I don't try to turn the engine over. It'll rise to 58, hold for maybe 2-3 seconds, then drop. Should it rise to 58 and stay there, even if I pull the key off?

    Bad rrfpr? Bad fuel pump? I'm half tempted to replace both, just in case

  9. #9
    moparguy's Avatar
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    Quote Originally Posted by samphysicsman View Post
    @splishsplash and @1tommygunner1927 - I see exactly what you guys are saying. The pump primes up to about 58, but immediately drops back down to 0 if I don't try to turn the engine over. It'll rise to 58, hold for maybe 2-3 seconds, then drop. Should it rise to 58 and stay there, even if I pull the key off?

    Bad rrfpr? Bad fuel pump? I'm half tempted to replace both, just in case
    I experienced a similar issue this year, turned out to be the second ground reference for the pump. It would do the same thing rise to 58 and then drop.

  10. #10
    Got Boost? psycho rxp's Avatar
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    Isnít there a check valve built into the fuel pump itself, On the pressure side?
    Did you install the relay for the Riva fuel pump?


    Iíve had one go bad before and had similar issues. The rough idle is likely due to the stage three cam, and Engine vacuum is going to fluctuate with that one

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