Noise supression / shielded spark plugs and wires?? - Ranger-Forums - The Ultimate Ford Ranger Resource


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  #1  
Old 09-02-2004
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I am getting this god awful RF interference coming from my ignition system and it is driving me insane. I is one of three things:

1. Coil pack
2. Spark plug wiress
3. Spark plugs

So, what I need to know is what is the best set of spark plugs and wires when it comes to shielding and noise suppression? I'm saving the coil pack for last since it is probaly the most expensive.
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  #2  
Old 09-02-2004
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well your most likely not getting RF from your plugs, and probably not your coil. the wires are the most likely culprit, but with todays technology, there shouldnt be much RF leaking out of them. the oem wires are actually pretty good, and not really worth and upgrade. i assume youre getting the RF in your stereo or CB or whatever, i would make sure none of the wires for any of that stuff are near the wires.
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  #3  
Old 09-02-2004
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Proximity of wires unfortunately has nothing to do with it. I wish it were that easy. The noise is getting radiated like the spark plugs/wires/coilpack is a giant transmitter. Anything with an antenna inside or around the truck will pick it up. Even a portable radio with no attachement to the truck will pick it up.
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Old 09-02-2004
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Well, the plugs are the source (with the spark generating a wideband RF noise) and the wires and coil and all are the radiators.

Ford's DIS in the Ranger is TERRIBLE that way. There are a few solutions.

1. Many years ago, hams did take the braid off some RG/8 coas, and smooth it over the spark plug wires, grounding it at one end or both (depending on what worked best, lol).

2. I have snap on ferrite chokes on all 6 spark plug wires. This cut it about 50%, but did not eliminate it. There are different types of ferrite material that is better for some frequency bands and it's possible a different snap on toroid would have been better -- but the ones I got I bought surplus from http://www.allelectronics.com and you never know quite what you're getting.

3. Have a better radio. Good ham and CB radio's have noise blanker circuits that work. Both my Maxon CB and my Kenwood ham rig have them and it's like NIGHT and DAY. Get a radio with a noise blanker or "ANL" circuit (different names for the same thing).

If it's definitely ignition noise, that's probably it. Ford is famous for fuel pump noise as well -- it's a more constant buzz that is somewhat affected by motor speed, but not much.

The reason it's so bad is the same reason Ranger's don't benefit from aftermarket ignitions -- the DIS is really "hot". The resistor in the plug (or the "resistor wires") that is supposed to help limit the di/dt when the plug fires is a bit small for the voltage of the ignition coil. So when the plug fires there is a sharper rise time, creating much more noise.

Also, make sure you have your radio's grounded well. It's part of the reason I am so fanatical about NOT using "body" ground but instead running an 8 ga wire back to the battery. There are too many circulating ground currents and noise in a modern electronic automobile for that to work well -- especially at higher frequencies.
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  #5  
Old 09-02-2004
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The noise is coming in ALL the radios the same. That is two motorola two-ways and the Icom dual-band. I have never seen a commercial two-way radio with a noise blanker on any band but low band. They don't give you that option on VHF, UHF, and 900Mhz.

Are there different splark plugs that will create less noise and different wires that won't radiate it as bad??
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Old 09-03-2004
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Maybe you have a cracked insulator on one or more plugs.
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Old 09-03-2004
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I assumed erroneously that you were getting the noise on an AM/SSB type radio rather than FM because your problem is unusual.

My experience with VHF radios that have noise is that it is almost ALWAYS bad antenna grounding or bad power grounding. Despite the noise on my HF/CB rigs, I have no noise on my Yeasu or ICOM VHF rigs. The Yeasu is for voice, and the ICOM for APRS/packet. How did you ground the rigs and antennas?

Dave and Julie (one or both, lol) make a point but I still don't think you would get it on a VHF or UHF FM rig. See if you can get a feel for the repeat rate of the spikes. If it seems "low" it might indeed just be from one cylinder. Still, I expect you'll find more problems with grounding than with received RF -- especially since ALL your higher frequency rigs are doing it.

Is the noise "spikey" sort of noise? Or is it more of a rush or roar or whine? If it's not an "impulse" noise it's not the ignition but more likely the alternator or fuel pump. Do you have an electric fan? I guess the noise is present the entire time the engine is running?

As far as wires and plugs, about the only thing you can do is shield or reduce the rate of rise in the current using "resistor" plugs or wires. I don't think changing the wires or plugs will do much if it's as bad as you say. It still sounds like a bad ground to me.

As a sidebar: FM rigs are inherently INSENSITIVE to impulse noise. The limiter ahead of the demodulator provides this function and pretty much gets rid of all noise as long as the signal level is over a certain level. That's why it sounds to me like the noise is getting in by another route.

One last thing to check is the ground strap from the engine to the body. It could have come loose and be giving you problems somehow.
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Old 09-03-2004
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All my antennas are grounded quite well. They are all either roof or L-Bracket NMO mounts. They are grounded and connectors soldered. The radios are grounded properly as well. John, even a portable with no connection to the truck picks it up. It is a popping scratchy sound that rises and falls with RPM. No the fuel pump and not the typical alternator sound.
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  #9  
Old 09-03-2004
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Wow. Then I'm now leaning more towards the "defect in the ignition" theory like Dave and/or Julie. I have no such noise in my truck (which is only a 3 liter, but the ignitions are virtually identical).

Has it been that way since day one? Any engine performance problems or changes? I'd check that engine ground strap for sure.
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  #10  
Old 09-03-2004
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Plugs can be cracked and still stay in one piece and look fine, even though they aren't fine.
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  #11  
Old 09-03-2004
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Well, there was always noise but it was one that a noise filter on the power feed fixed. This problem cropped up after I added the 900 radio and did some minor wiring changes. Nothing I did would have caused the noise and nothing I do changes it. So I'm thinking it is just coincidence. I guess I'll start with wires then plugs and see what happened.
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  #12  
Old 11-03-2004
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well i dont know if you still have this problem fireranger but i had it with my cobra 29 cb only when i floored the engine i could hear engine noise. so the other day we had a 2 way radio guy in at work and i had asked him and he told me that most cbs come with a suspresser something that is spose to take care of that noise. but anyways i went to radio shack and got me a supreser and i do not get any noise coiing out of my cb like windows or when i floor it now. also the guy said that it is due to the windings in the alternater maybe this will help
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  #13  
Old 11-03-2004
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Noise filters on the power feed like your suggesting did not help since the nosie was not being picked up through the power feed.

I did get it fixed. It appears to have been a bad spark plug wire. After replacing them all, it is fine now.
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  #14  
Old 11-04-2004
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Good to know! Glad you got it fixed finally. I figured it was a defect in the ignition somewhere.
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