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Loosing fuel pressure above 4,000 RPM

This is a discussion on Loosing fuel pressure above 4,000 RPM within the General Help forums, part of the LSx Technical Help Section category; Car on dyno trying to get tuned with EFI Live. Turns out I'm loosing fuel pressure above 4,000 RPM's. At ...

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    Loosing fuel pressure above 4,000 RPM

    Car on dyno trying to get tuned with EFI Live. Turns out I'm loosing fuel pressure above 4,000 RPM's. At idle and below 4,000 Fuel pressure is rock steady at 58 PSI.
    When making a pull It drops 10-15 psi at 4,000 to 4,200. By 5,000 its down over 20 psi (reading around 35psi). With a mechanical gauge on rail.
    I have a 99 Camaro SS With a Racetronix Pump and Hotwire Relay Kit. I put a new GM filter on 1,500 miles ago when pump was installed. Car is running 42 LB injectors, rest of fuel system is stock. Filled tank to make sure module was not running dry. Nothing changed with full tank. I don't know where to start with this problem, Please Help!

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    If you are running 9.13 in the 1/4 then you might be beyond what the F99 single in-tank pump can support. Please contact your Racetronix vendor or support@racetronix.com with all your details and full contact info for further help.

    Thanks.

  3. #3
    Veteran 0rion's Avatar
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    a list of mods would be handy. Like was mentioned you may need a booster pump or dual pumps.

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    Stock Shortblock, ported heads (300 cfm), Comp Hydraulic 224/230, 1.8 rockers, LS6 intake, ZO6 Mass air, air lid. 42LB injectors. Very mild combination. On dynapack it was 400HP to the wheels (through a 9") at 4,800RPM at 15:1 A/F.

  5. #5
    Slow'er'Ass Mr. Luos's Avatar
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    Quote Originally Posted by 9.13onMotor View Post
    Stock Shortblock, ported heads (300 cfm), Comp Hydraulic 224/230, 1.8 rockers, LS6 intake, ZO6 Mass air, air lid. 42LB injectors. Very mild combination. On dynapack it was 400HP to the wheels (through a 9") at 4,800RPM at 15:1 A/F.
    WAY Lean...

    Does it go lean on the wideband? What kind of fuel pressure gauge? Sender?

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    That is on the wideband, datalogged. Mechanical gauge on rail, no sender.

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    Slow'er'Ass Mr. Luos's Avatar
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    Is the pump getting proper voltage?
    Check lines for a crimp near the pump.

  8. #8
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    Didn't drop tank yet, need to burn out full tank of gas (roads are snow covered here) Voltage good everywhere I can check.

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