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Holley sniper EFI


jim's 70

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The tank came from Holley, sometime it starts up right away and then it will take 1 minute or two before it will restart but when it fires it runs good. My son in-law Jamey is doing some research and I  will forward him these ideas. thanks guys

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I wondered if the ecu being right on top of the engine and in the heat like that contributes to the problems. That’s a lot of electronics and circuits in a small package that has to deal with vibration and thermal events

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I have not taken the time to play around with it. Nice weather had the gold course calling my name several days this week along with mowing and playing around in my wood shop. My son in-law Jamey has done some investigation into the problem. The likely source of the problem is the Taylor Spark Plug Wires being one of the main issues, According to one article he found that 90% of the time they are the problem. Several sites recommended MSD Super Conductor or Magnecor wires. Right now money is a minor snag in really getting into the solution.

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  • 1 month later...

Well we got the Sniper EFI working great  last Saturday. Driving home it died twice, the first time it started after sitting for a minute, it sputtered twice but did not die. The second time it died and we ended up flat bedding it home went out Sunday morning and it fired right up, checked the pickup coil in the HEI, good, Rotor good, Dist cap good.  I am getting a fuel pressure gauge to monitor that and to see that maybe there is a problem with the fuel deliver. The only other thing that comes to my mind is the MSD Box is starting to fail but I have never heard of that happening but there are always first for everything. My son in-law Jamey are stumped. New MSD Super Conductor Plug wires, new AC Delco 45TS plugs. The old Taylor plug wires were failing and one article we seen said Taylor Wires are know for causing some problems with the Sniper

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  • 4 weeks later...
  • 7 months later...

Still sorting things out. Every time I think I have it working correctly it messes up again. Talked to Holley support and he gave me a list of things to check which I am now heading out to the garage to start looking at. The idle is spot on when I first start the car then it will jump up 700 rpm. Going down the road the engine will stutter and the IAC jumps up to 36 when normal is 2 to 10. Checking the IAC control for carbon buildup, inside of Dist cap for carbon deposits and the voltage is staying in the 14 volt neighborhood

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Had similar problems with Sniper, wouldn't run consitant, fouled plugs, flooded, misfired and then some days run great. My son was to talking to a friend of his and he reccomended wraping the TB harness (each group separaley) with foil tape (I used heating duct tape, very thin and easily cut into strips) and then wrapped with a good quality tape ( I am looking for mfg) separate lines as far as possible from each other on install. I also sprayed the bottom of the air cleaner housing with rubber under coating. All this if to stop the electronic interference.

I have not had a hicup since I did this a year ago. The frustraiting  part is that Holley is aware of the problem and don't care to address it.

I will let you know the brand name of the tape as soon as i find it.

16849467264256137062374065605.jpg

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19 hours ago, Leghome said:

Thank you Grant I just ordered two rolls

 

What type of ignition you running, Larry?

I'm going thru some MSD/Holley drama right now with my EFI setup, but it's with their 'Dual-Sync' distributor, used to control the timing. Apparently they're a known problem with bad modules, as well as the MSD 8366 small cap hei distributor.

Random, intermittent cut-outs, no start sometimes, then other times it runs like a champ. I just took some log files and O-scope traces and verified what looks like crank signal failures. Gonna swap out the distributor to see if that cures it. 

EDIT: New distributor fixed it. Verified failure and repair with scope traces. Going to contact MSD about repairing the bad one, as the Z/28 has the same one in it, and the clock is already ticking when that one will fail.

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3 hours ago, jft69z said:

What type of ignition you running, Larry?

I

GM HEI with a MSD Multi Spark Discharge system that I sent in last fall and had rebuilt.  Thought about going to the distributor that inter acts with the Sniper but $770 is a little out of my price range at the present time

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22 minutes ago, Leghome said:

GM HEI with a MSD Multi Spark Discharge system that I sent in last fall and had rebuilt.  

That at least eliminates one variable.

It's nice to have the computer control the timing, but also one more potential failure point, as I found.

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  • 2 weeks later...

Car ran good for a week or so then wham all messed up again. Wrapped the wiring with the tape Gary recommended and it still was not right. The next step was to remove the O2 sensor, it was carboned /oily residued up, cleaned it up and reinstalled it and presto hot diggity dog it runs like it is new again. Hard to believe that one little thingamabob could cause so many different scenarios  that kept Ole Red from running. Now I know what to look at first if it acts up again.  Also going to get a spare to have with me if it acts up while traveling.

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10 hours ago, MC1of80 said:

Glad you found the issue. I have one question though. What caused the O2 sensor to get carboned/oily in the first place? 🤔

My thoughts exactly 

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I really do not know but When I put new plugs in last fall No. 7 was fouled some.  I did learn a new trick or technique today use tidy bowl or some other toilet bowl cleaner instead of the expensive stuff. Learned that form a long time mechanic friend today at the car show where we got another top 30. That is three weeks in a row for Ole Red

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