kansjfr

I know this is a long shot, but about a year ago I added Holley Sniper fuel injection to my '68 442 4-speed convertible. It ran pretty good for several months, and then it started acting like it was hitting a fuel cutoff at very low rpms (2k). Really hard on the drive train. I called Holley's tech line, waited 45 min on hold and then the tech told me two things: 1) I had to mount the electric fuel pump BELOW the new fuel tank so that the fuel could drain down to the fuel pump and 2) that radio frequency interference was causing the cutout of the fuel (!?). Neither theory seemed plausible to me but hey, they're the manufacturers of the system. The fuel pump is mounted about level with the fuel tank now. Any help/comments/suggestions would be appreciated.

joe_padavano

The pump should be as low as possible. Electric pumps like to push fuel, not pull it. Also check to see if the inlet sock in the tank is deteriorated or clogged. Have you changed anything in the wiring since the original install, like added a stereo or gauges? EMI is a credible problem.

myhoney

My 2 cents.
I will start with I did not install my system, it was done by my shop that does all my repairs.
The interference that Holley speaks of is a real thing, I had stumbling and a pop back through the throttle body starting after about 1000 miles.
The fix was a magnet that was installed on the positive cable from the alternator to the battery.
This instantly improved off idle response and the popping I was getting.
The magnet that was installed is similar to what you would find on the signal cable on a computer monitor, they just snap on around the cable.

Hope this helps.

matt69olds

I have a Sniper on my 69. You have my condolences dealing with Holley tech support.

I had the first Sniper throttle body on my car for 2 years. I had more than my share of learning issues, and also in my opinion issues brought about by the consumers being unknowingly part of the “design and development” team. I’m awaiting a reply from Holley as I type this for my one month old replacement throttle body. 😡

Have you done any reading on the Holley forum? Have you recorded a data log? Even though the Sniper is advertised as self tuning, it takes LOTS of driving, many cold starts, lots of miles in various weather for it to really dial itself in.

Im convinced Holley tech blames many of the glitches on EMI. If the car ran well and then randomly starts running like crap, with no vehicle changes, and a through inspection of all wiring and vacuum hoses, I wouldn’t be the least bit surprised if it’s a internal issue. Make sure all the wiring is done correctly, not routed anywhere near the ignition system, then ask some more questions, or take it back to the shop that did the install for another look over.

kansjfr

Thanks for the responses, guys. Joe, I didn't make any changes after the original install. I'll have my mechanic re-mount the fuel pump, and try the magnet trick Where can I get one of those magnets? Thanks again, guys. By the way, I agree about the Holley techs.

Olds64

A magnet used to block EMI is called a choke. Use one like this. They come in multiple sizes and styles:


Here's a good thread on the Holley forums:

https://forums.holley.com/showthread...-Installations

myhoney

Here is a link on amazon for an assortment.
Good info from Olds64

kansjfr

Thanks for the links,guys, Very helpful.

1970 98

Installed a Holley Sniper Throttle body on my 455 in 2019 and fought it for a year before getting it right. Understand your pain with contacting Holley tech support. Had many issues but finally resolved.

Have you checked the fuel pressure? should be 60 PSI to the throttle body
Are the fuel filters clean and transferring fuel? On mine, the pre fuel pump filter is 20 Micron (NAPA 3033) and the post fuel pump is 10 micron (NAPA 3482).
Do you have a data log of the "fuel starved" condition? If so, I can look at it if you want.

My intermittent problem was resolved by replacing the ECU (the main Throttle Body). Those internal fuel injectors have problems at times.

Will write up my experiences and lessons learned with Holley Sniper installation very soon. Was quite the adventure!

Cheers

kansjfr

How did you get a new throttle body? The guy at the Holley tech line told me it wasn't available separately, like I was going to have to buy a whole new Sniper system.

1970 98

In my case, I had bought the entire Holley Sniper kit for the initial installation. The new throttle body was replaced under warranty. After reviewing my message, my words should have been more clear. My bad. Also, at that time (early 2019), you could buy an individual throttle body.

6T9442Drop

Oh man. I hope I don’t have these issues. I currently have a Fitech(bough the car with it) and have a brand new Holley Sniper ready to put on. I bought it because INOBODY wants to touch the Fitech in terms of doing a complete tune! I live in the SF Bay and not one shop wants to fiddle with a Fitech.

dc2x4drvr

I’m just fiddling with my Sniper QJ installation, the Holley forum has a lot of user threads that help with various issues.
Site
https://forums.holley.com/forum.php

6T9442Drop

Thanks for sharing. How do you like your Holley Sniper so far?

dc2x4drvr

There are a few tuners who can custom tune EFI installations long distance...that’s my plan.

derone

Fuel injection systems like 'clean' power. If you're running a mechanical voltage regulator lose it and either find a transistorized one or another alternator with one built in.
I choose the later route and left the original regulator but disconnected it and made bypass jumpers across the connector for it. Should be many articles on how to do it.

Amplitude

I worked in the 12V industry for over a decade doing remote starts, custom high-end audio systems, and just about anything you can imagine that might get hooked into a car's electrical system.I can give everyone a few points of advice on EMI, RFI, shielding, and electrical gremlins in general.
Oh, I've also built and installed several Megasquirt DIY systems, a few MSD Atomic LS kits, and a retrofit LS2 with a TBSS ECU and a custom harness. Now I design commercial Audio Video systems for distance conferencing systems and for sports stadiums. So yeah, interference can still be an issue.

• Part of the job of the car battery once running, is to filter any residual AC ripple produced by the alternator
  • So make sure you battery is in good shape, and ensure that your primary power for the sniper is coming directly off of the + post of your battery.
• You can also use a 12V car audio 1/2 farad capacitor(easily available) or smaller if you can find it to act as an inline filter for your accessories and also as a voltage stabilizer. It's job is to provide extra power when there is a sudden excessive load, or a sudden drop in supply.
• As mentioned before, clean power is good power. You can buy a handheld oscilloscope for about $200 that will let you look at your 12V signal to ensure no errant AC waves are present.
• Aftermarket EFI ECUs are incredibly sensitive to proper voltage. The MSD will not even run with anything less than 12.6 volts.
  • Now your battery might be able to crank the engine over just fine, but it could still have a short between cells. So check your battery voltage during cranking, or just turn on your headlights and watch your battery voltage slowly drop. If all of the sudden it drops by around 2V, you've got a bad cell. Since a 12V automotive battery is comprised of (6) 2.11 volt cells.
• Make sure you plug wires call out that they have shielding to prevent electronic interference. Also make sure they aren't damaged or cracking in any way. A cracked distributor cap can also cause issue.
• Don't ground your coil or EFI ECU to your manifold.
  • Sometimes running a ground from EFI directly to the battery will alleviate problems
• Check all of your grounds
  • Engine ground to frame
  • Battery to frame
  • Body to Frame
  • Sometimes Engine to body.
  • Make sure your ground connections are properly terminated with all paint stripped from the location, a ring terminal crimped onto the wire, and I like to utilize a star washer that can get a good bite and stop the ring from spinning. After I ground something, I will shoot it with a rust preventative paint.
• To check for ground issues, you can do a voltage drop test.
  • Use you DMM and perform voltage drop tests across your circuits.
    • YouTube Voltage Drop Test and Explanation.
• Finally, if you really believe that RFI or EMI is the culprit, you can purchase several types of shielding material such as MUMetal to isolate the Sniper throttle body ECM from the source.
• If that still doesn't work. There are devices such as the RF Explorer: available from amazon that can help you identity and sniff out the source of the interference. But be prepared to purchase a very narrow coverage antenna, and spend some time learning more than you ever though you needed to know.
• As a final and somewhat fun hail mary test. you could build a simple wooden box frame that will fit around the sniper unit, and can be secured under your hood. Wrap five of the six sides with a fine copper mesh, thus creating a Faraday Cage that you can place over your sniper system to isolate it from almost all possible radiated interference. Now if the interference is inducted, this won't fix it.