View Full Version : Engine symptoms
yahrt
10-13-2022, 05:19 AM
Hi all, I am running a BP 347 with a Sniper EFI from Forte, intank fuel pump from Breeze. Have been trying to research my problem but cannot seem to find description of he same symptom, which is: complete engine hesitation wherein the tach momentarily drop to zero followed by recovery, usually occurs during acceleration and associated with some backfiring, and seems to occurs less frequently after the engine has been run for a while but never completely resolves. I have 300 miles on so far. I am guessing it is electrical interference but would like verification that this is most likely before trying to resolve. Thanks. TY
KDubU
10-13-2022, 05:59 AM
Sounds more like a fuel issue to me but I am no expert. Someone will chime in here on best triaging steps.
Norm B
10-13-2022, 06:02 AM
I had a similar issue. The Holley tech told me to try wrapping the distributor with aluminum foil. That cured the problem. Made a permanent shield out of some thin aluminum sheet and covered it with a Cobra distributor cover.
HTH
Norm
Nigel Allen
10-13-2022, 06:10 AM
A momentary zero tacho reading indicates loss of ignition pulse, not a fuel issue. Take a good look at your distributor and ignition module connectors. With engine running, do a tap test and wiggle test of all ignition related wiring and components. Check that no pins have pushed backwards in their receptacles.
Best of luck.
CraigS
10-13-2022, 06:16 AM
A momentary zero tacho reading indicates loss of ignition pulse, not a fuel issue. Take a good look at your distributor and ignition module connectors. With engine running, do a tap test and wiggle test of all ignition related wiring and components. Check that no pins have pushed backwards in their receptacles.
Best of luck.
Agreed. Also think back to the position of your wiring runs for the efi and the ignition. Sometimes signals can get messed up when wires are run closely together.
Geoff H
10-13-2022, 07:22 AM
What are you running for a distributor?
BradCraig
10-13-2022, 10:15 AM
I would start with verifying all your connections, then collect a Sniper log to perform analysis. In the absence of anything "wrong", there are some basic tuning items you can and should do on the Sniper. They aren't nearly as self-tuning as Holley advertises!
Norm B
10-13-2022, 10:15 AM
As others have asked, what distributor and ignition system are you running and where are the components located? Holley wanted any ignition components as far from the Holley ECM (the front of the unit) as possible. Your choice of of air cleaner also makes a difference. Holley wasn't happy with my "COBRA" oval air cleaner that overhangs the distributor. Manage to keep that by shielding the distributor.
Norm
yahrt
10-13-2022, 01:57 PM
Thanks for all of the helpful comments so far. I am running a Holley Distributor Sniper EFI HyperSpark system and using the oval Cobra air cleaner. Looks like the first thing to try is shielding the distributor.
wallace18
10-14-2022, 08:41 AM
The Sniper with the Oval Cobra air cleaner will cause a bunch of issues. Blueprint started to send a EMI shield with this setup. I ran into it a few years ago and switched to FITech. No issues at all after the switch. Hopefully some shielding will fix your issue. Best of luck.
Tuftster
10-14-2022, 07:52 PM
Had the exact same issue with my Sniper. Had to reroute the wires away from the spark plug wires. It's very sensitive to EMI.
Question: When you wired the Sniper, did you de-pin the unused wires from the Sniper's two main connectors (7-pin and 10-pin) and install silicone terminators where the empty ports are? As others have mentioned, EMI (Electro Magnetic Interference) is a very well-known issue with the Sniper. For what it's worth, I was able to run the Sniper with the oval air filter and did not experience EMI issues. I was also running a standard distributor and coil with all Sniper wires well away from the ignition components.
yahrt
10-15-2022, 02:34 PM
Did the experiment of wrapping the distributor in aluminum foil, ran perfectly no issues. So what is the permanent, more aesthetically pleasing solution?
Did the experiment of wrapping the distributor in aluminum foil, ran perfectly no issues. So what is the permanent, more aesthetically pleasing solution?
If you haven't done the de-pinning, that should be your next step. Each one of those loose wires acts like an antenna that can introduce noise into the ECU.
yahrt
10-15-2022, 04:23 PM
The harness was de-pinned of the extras during initial install so that is not the issue.
Next would be to make sure your ignition wires are not running alongside the other EFI wires. What air cleaner are you using? Do the symptoms clear up if you remove the air cleaner? You can also shield the wires themselves.
https://www.amazon.com/Tinned-Copper-Braided-Sleeving-Diameter/dp/B01BIBQESG/ref=sr_1_2?crid=1BLG8KCUTW8F3&keywords=automotive+wire+shield+for+EMI&qid=1665869726&qu=eyJxc2MiOiIyLjA1IiwicXNhIjoiMC4wMCIsInFzcCI6IjA uMDAifQ%3D%3D&sprefix=automotive+wire+shield+for+emi%2Caps%2C92&sr=8-2
Norm B
10-15-2022, 08:32 PM
To make the shield for my distributor I used the thin soft aluminum sheet available in the auto body repair section at my local parts store. I clamped a round block of birch firewood, the same diameter as my distributor in a workmate, and beat the aluminum into the shape I wanted. A few relief cuts were needed to get the shape I wanted and I taped those up with aluminum duct tape. Covered the whole mess with a “Cobra” distributor cover from eBay. It might be overkill but, I grounded the shield to the frame with a wire.
HTH
Norm