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Thread: Sniper cutting out with load at 3/4 throttle & up.

  1. #1

    Default Sniper cutting out with load at 3/4 throttle & up.

    I was reading through most of the posts on the Holley forum, but didn't see any similar to my problem. I got mine a few months ago, and installed it on my already great running newly rebuilt 468 BBC with a Pro Comp dual-plane intake, MSD Billet Crab Distributor, 6A box & 830 Quick Fuel carb. Since the truck ran great with the carb, I left the timing alone and didn't hook up the timing portion of the Sniper. The install went super smooth and it fired right up. I kind of left it alone for a while because it's in an old C10 without A/C and its been 110°F-120°F the past few months in AZ. So one day I took it out in 100°F weather, and just decided I would bite the bullet and drive it as much as I could stand it (about 100 miles). It idles great, runs smooth, but when you give it full throttle it stumbles and seems like it's running out of fuel. Any suggestions?

  2. #2

    Default

    Have you checked the injector duty cycle when it stumbles? Maybe it is lacking fuel. If the duty cycle goes close to or over 100%, you have a fuel flow problem.

  3. #3
    Join Date
    Dec 2009
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    Default

    Quote Originally Posted by chadzilla6500 View Post
    ...but when you give it full throttle it stumbles and seems like it's running out of fuel. Any suggestions?
    Yes, provide data, not just the symptoms. Does the Data Monitor/Gauges indicate a rich or lean condition when this occurs?

    Quick Datalogger Information:
    Always provide data, not just symptoms. Is the AFR & ignition timing optimized? Overlay the datalog onto your Global File.
    Ensure the Target A/F Ratio table is properly programmed for your engine. Ensure the ECU is "Learning" (Learn Table LINK).
    Scroll through the datalog to the problem area. Then look exactly where this happens on the Base Fuel & Timing Tables. Scrutinize:
    RPM, MAP, MAT, TPS, CTS, IAC, Target AFR, AFR Left, CL Comp, Ignition Timing, Duty Cycle, Fuel Flow, Fuel Pressure & Battery.

    Using the Holley EFI software (LINK), look at where the live cursor moves to during this occurrence, and
    manually tune that area of the Base Fuel Table (enrich or lean) & Base Timing Table (optimize ignition timing).

    I find the most helpful datalog function, is overlaying the datalog on your Global File.
    I'm in the habit of using the datalog Overlay feature every time I review a datalog.
    Click on "Datalog" (on the top Toolbar), "Activate Overlay", then "Open Data Log".
    You can literally "playback" a recorded event, and watch it as it happened on any screen.
    Minimize (shrink) the datalog window, and move it to the bottom of any Global File screen.
    Then click & scroll anywhere on the datalog, and watch it playback on your Global File (EFI software).
    http://documents.holley.com/techlibr...9r10543rev.pdf (Holley EFI Datalogger Instructions)
    https://forums.holley.com/showthread...s-amp-Datalogs (Datalog & System Log Information - Read "NOTES")
    https://www.youtube.com/watch?v=iqHO...C6FEA0BB99AF17 (How To Record & Email A Datalog)
    https://forums.holley.com/showthread...7531#post77531 (Closed Loop Datalog Tuning - Posts #2, #4 & #6)
    May God's grace bless you in the Lord Jesus Christ.

    '78 BRONCO: 508" stroker, TFS heads, 11:1 comp ratio, Dominator MPFI & DIS, cold air induction, Spal dual 12" fans/aluminum radiator, dual 3" exhaust/Magnaflow mufflers, Moroso vacuum pump, Accusump, engine oil & trans fluid coolers, 100HP progressive dry direct-port NOS, A/C, LenTech Strip Terminator wide-ratio AOD/2500 RPM converter, 3:1 Atlas II, modified Dana 44/60-lockers-4.10s, hydroboost/4-disc brakes, ram-assist/heim joint steering, Cage long radius arms, traction bars, 4" Skyjacker lift, 35" mud tires

  4. #4

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    FYI: I contacted Holley tech support and got Jason on the phone. He was very professional and KNOWS what he's talking about. We spent a week trying different things. After buying a fuel pressure gauge & fittings, I put my GoPro under the hood and drove it. I noticed there was almost zero pressure at 3/4 & up throttle. Jason thought it might be a clogged filter. Since you can't see inside them I decided to take my filters apart via band saw to look for debris. They were fine and only $15 for the pair from NAPA. He ended up sending me a new pump. My truck runs so awesome now, better than it EVER did with that Quick Fuel 830 carb.

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