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Thread: Sniper intermittently cutting out, new install.

  1. #1

    Default Sniper intermittently cutting out, new install.

    New Sniper EFI with rail mounted Holley pump install, on prior good running mildly built small block Chevy 350 in a '56 Chevy pickup, using preexisting MSD Pro Billet distributor with locked out rotor/phased, and preexisting good running MSD 6A box.
    After install of Sniper with all other ignition components as they were the EFI fired right up, ran well through warm up cycle, I confirmed timing matched Sniper command, adjusted IAC to 7-8. Ran truck up street, ran great, put about 2 miles on it, came to a stop sign at idle & engine quit like key was turned off. Monitor screen did not fluctuate & still showed all readings. It fired right back up & ran well for another couple blocks. Then every once in a while it would blip/try & stall, but would stay running if the truck was at speed. When it does the symptom, the TPS reading goes red & shows -20, the AFR, A/F & MAT goes red at about the same time, but not all 3 in sync. The TPS seems to be the first one to go red & stay red the longest. When the engine comes back in, the IAC is hissing like it's on an initial start, the screen stays lit up & RPM stays in line with actual engine RPM during symptom (1,800 RPM, etc.). I disabled Closed Loop & same symptom present. I double checked all my connections & wiggled wires/connectors back in the shop with the truck running, but could not reproduce the symptom on demand. Powers & grounds are clean & secure, wires are run as far away from plug wires as reasonable. Any ideas? Thanks.

  2. #2
    Join Date
    Dec 2009
    Location
    Connecticut
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    18,662

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    You'll have to record a datalog of this occurrence, and email it to Holley Tech Service (LINK) for analysis (since the Sniper EFI software isn't quite available yet).
    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

  3. #3

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    Thanks. I'll try that, next day it's not raining/snowing sideways.

  4. #4
    Join Date
    Oct 2016
    Location
    Middle River, MD
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    249

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    The "fix" for mine (having the exact same issues), was to remove the adjustable rotor and use the regular stock one and let phasing fall wherever. Has run fantastic ever since, has never stalled, hesitated, fluttered, or misfired since. Doesn't make sense, as per the experts, but it works, and that's all that matters.

  5. #5

    Default

    Wonder if it has to do with the rotor itself causing RFI? Possibly not insulated enough? I had the same issue that eventually worked its way into a won't even run problem. Ran fine with stock cap, but once I put on the indexable rotor it started running worse & worse. Now I think the pickup took a dump and waiting on a new one. Tech support said RFI interference causing my RPM signal to glitch & screw up the fuel map, causing it to stumble & stall. Twisted the wires and added shielding over them, but didn't help. Another doesn't make sense, but a thought.

  6. #6

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    I installed the standard non-adjustable ignition rotor this morning, and the spark is way too soon as viewed through the window in the cap. Also hard start & sounds a bit scattered when running. Scrolling through the adjustments, I saw "Inductive Delay" option. Could this adjustment be used to delay the pickup & "phase" the non-adjustable rotor?

  7. #7
    Join Date
    Dec 2009
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    Connecticut
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    The Inductive Delay synchronizes the ignition timing at higher RPM. It must be properly adjusted. Ignition timing synchronization is very important.
    http://documents.holley.com/199r11031r.pdf (Holley Sniper EFI Instruction Manual - "Inductive Delay", Page 29)
    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

  8. #8

    Default

    Quote Originally Posted by Danny Cabral View Post
    The Inductive Delay synchronizes the ignition timing at higher RPM. It must be properly adjusted. Ignition timing synchronization is very important.
    http://documents.holley.com/199r11031r.pdf (Holley Sniper EFI Instruction Manual - "Inductive Delay", Page 29)
    Thanks, I did not adjust the Inductive Delay, and high RPM is great.

  9. #9

    Default

    I ran it a bit again today between snow/rain, it died once at idle after 20 minutes of run time & immediately the TPS read red & - 20%. I had wondered if the -20% TPS reading on prior times during symptom, was me letting my foot off the throttle after the symptom, and the ECU resetting the TPS to 0 where my foot was on the throttle (+20%) during the symptom causing the -20%. But today I was at idle in park in the driveway with my foot off the throttle, it died & immediately the TPS went red & -20%. It's so hard to tell what's happening at cruise or at speed, as it's just a quick blip/will stay running, but it will cause a stall when at idle. I do have another Sniper coming on next week for my '67 Firebird 400, so I will have the availability to compare/swap parts if Holley can not help.

  10. #10
    Join Date
    Dec 2009
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    Connecticut
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    Quote Originally Posted by orcas tow View Post
    Thanks, I did not adjust the Inductive Delay, and high RPM is great.
    It doesn't matter if high RPM "feels" great. What matters, is if the timing is synchronized (Sniper EFI touchscreen & timing light).
    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

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