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Author Topic: Ignition Noise - Cannot eliminate: 94 Toyota Picku  (Read 1169 times)
KB7TEF
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Posts: 16




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« on: January 29, 2003, 11:53:19 AM »

Hi!

I have just installed my Kenwood TS-B2000 in my 1994 Pickup with a Tarheel screwdriver.  The antenna works well, as does the radio when the ignition is off. When on, I get about an S7 of noise.

My radio is grounded inside the cab.  The antenna is also thoroughly grounded.  If I disconnect the antenna, the noise is gone eliminating conductive RF noise.  The problem is not the fuel pump.  As my speed increases, so does the noise.  If I take my foot off the gas, the noised reduces a bit.

I have put ferrite around the power cable at the source and near the radio.  The 12V cable is to the battery, the ground is in the cab.  The noise is apparent on all bands when the screwdriver is tuned to that band.  

Things I am going to try, but have my doubts:
1. Ground the tail pipe.
2. Ground the body to the Chassis in several points.

From there I am not sure where to go.  I read an article in Jan/Feb QST 2000 that was very helpful, but being a fairly new HAM I do not have the expertise to carry out his suggestions.  They are very involved and require a lot of equipment.

Does anyone have any other suggestions?  Magnecor wires?  Ferrite chokes around the spark plug wires?

Steve
KB7TEF
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K5LXP
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« Reply #1 on: January 29, 2003, 06:32:12 PM »

A tool I find particularily effective for sniffing EMI noise sources is an AM pocket radio tuned to a blank spot on the band.  By adjusting your distance from the source and turning the radio to change the direction of it's loopstick antenna you can determine fairly well where any noise is coming from.  Another effective tool I've used is a short 'sniffer' antenna made by stripping some coax back about an inch, cut the braid off and soldering the center conductor back to the braid to make a small shorted loop.  I used this like a 'wand' to pinpoint hot spots on wire harnesses and modules under the hood.  We're pulling for you, it's not an easy, fun or quick job.

Mark K5LXP
Albuquerque, NM
k5lxp@arrl.net
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KB7TEF
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Posts: 16




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« Reply #2 on: January 29, 2003, 09:18:41 PM »

HI,

That works well! I tried it, and found that under the hood is basically an electrical storm.  All kinds of RF from everywhere.  So, I am no better off than before I tuess.

Also,I checked and the tail pipe is grounded.

I have spent so much time on this now that I am about ready to sell all the equipment and stick to base operation.  Wow, I am at my wits end.
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K5LXP
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« Reply #3 on: January 30, 2003, 09:42:23 AM »

Sometimes they can be a real pain but stick with it and keep on trying different things.  It's not unusual to pick up a ton of stuff under the hood, but what of that interference is really the problem?  I can hold my AM sniffer radio near the digital speedometer in my car and hear a buzz, but it doesn't interfere with my HF setup.  The trick is to pick up on the pattern or sound of the interference on your HF rig, then sniff around and see where that sound is coming from.  If you're getting overloaded by other stuff, time to switch to the sniffer loop and pinpoint it.  If it still seems to be coming from everywhere, likely the wiring harness is radiating it.  I've had some success putting clamp-on split ferrites on cables exiting the various modules.  My worst offender in my current car was the harness going to the rear powering the taillights.  I picked up the noise just as strong in the trunk as I did under the hood.  If the noise is stronger on some bands than others, you might try hooking the sniffer antenna to the HF rig itself and pinpointing the noise that way.  Make up a bunch of copper braid grounding straps and start bonding everything- trunk lid, hood, doors, tailgate, several points along the exhaust, and (especially with old Fords) the computer module inside the car. There's no magic cure but being methodical and persistent is the key.  You may never eliminate noise completely but hopefully will reduce it to an acceptable level.

Mark K5LXP
Albuquerque, NM
k5lxp@arrl.net
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KB7TEF
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« Reply #4 on: January 30, 2003, 10:40:20 AM »

Thanks Mark for taking the time!  We need more Elmers like you around here Smiley

I can tell that a lot of noise is coming from the spark plug wires.  I tried using some ferrite beads around the wires but it had no effect.  I have heard that Magnecor sells shielded wires, but they are $130!!!  There has to be a better way...

I noticed that the toyota tailpipe had a metal bar attached to it and to the frame, so I am assuming that it is grounded.  Is grounding the key?  Or do I need to shield in some way as well?

And wow, the am band is much worse than ssb.  I should have known I guess.  I am quite sure that the majority of the problem is in the ignition noise...

Steve
KB7TEF
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W8JJW
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Posts: 90




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« Reply #5 on: January 31, 2003, 11:20:39 AM »

Isn't mobiling fun  though??

Couple things came to mind..because of the vintage of your truck, you need to check the existing wires and coils, etc for leakage. Once the wires are a few years old, they still work, but the internal resistance goes up. If your motor has a distributor cap, etc, try replacing them if they've been on for awhile. Make sure the wires are firmaly seated on the heads of the spark plugs and not doing a spark gap trick. Start the truck at night and look under the hood to see if you can see any visible sparking. Sometimes you can hear it..sounds like a ticking and is hard to differentiate from normal drivetrain noise.
If the vehicle is fuel-injected, I 've heard some ungodly noise from the injector pulsing and or solenoids. Toroids should help that.
I used some 1" tinned copper braid that I could slip the power leads through in the engine compartment and then grounded ONE end of the braid to the firewall where the wires go through.
I use a single point ground for the rig; meaning, the rig chassis, the trunk ground, the antenna mount ground all go to the same spot on the body. Yes, I did run a separate ground wire from the antenna mount itself, I did ground the trunk to the body (kinda hard in a pickup!)but you get the idea. I drive a Cadillac that has a lot of RF generaters due to the number of computer modules spread throughout the body area and I now have a S4 noise level, down from S9! I have no ignition noise now.
I need to say that I have a 706MKIIG that I have separated, so the main part of the rig is trunk mounted making the grounds as described above fairly short.

Good luck and let us know how you make out.

73 John
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KB7TEF
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« Reply #6 on: January 31, 2003, 11:32:25 PM »

Thanks to everyone for the tips.  Here is what I have tried:

Tonight I replaced the Distributor cap and the spark plug wires.  They had not been replaced since 1994.  I fired up the engine - no change. As much noise as ever.

I took my Kenwood THF6A HT and tuned to AM 3.8mhz and hooked a piece of 4' coax on it, exposed about 8" of the braid, etc., and started sniffin around the engine.  Sure enough, still a lot of noise coming from the engine area.  I noted that each of the spark plug wires were still quite bad.

So, I had read about shielding the cables with aluminum foil.  So, I individually wrapped each of the wires with foil, then bound them together and grounded them with some grounding strap.  I turned on the engine and took my HT and started sniffing.  The noise was substantially lower on the HT, so I turned on the HF rig excitedly.  How much lower?  Ha!  The s-meter was just over S9, so it actually got a bit worse.

As I continued to sniff around, those were the main points of noise.  Since the foil didn't work, I removed it and out some Radio Shack Ferites on the cables - no difference.

So, I am back to a complete loss.  

Steve
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WA4PTZ
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Posts: 528




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« Reply #7 on: February 01, 2003, 07:19:31 AM »

I own a '96 Toyota Tacoma and have similar problems,
although my noise level remains the same from
2 meters to 160 meters, ignition noise. I cured it
with a "CLEARSPEECH" speaker. That also cleared the
tuner-uppers on all bands as well as broadcast noise
and many other types of noise. It was worth every
penny.
 73 - Tim
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KB7TEF
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Posts: 16




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« Reply #8 on: February 01, 2003, 10:39:35 AM »

What does your S-Meter read?  I imagine that this could not have helped the noise you read on the meter?

Steve
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KF4EYR
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Posts: 14




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« Reply #9 on: February 02, 2003, 01:33:04 AM »

I had same problem,, I changed my spark plugs ,,ended noise,,, the problem was using cheap plugs,, I spent a few dollars more for them,, but the ignition noise is gone now,,, suppression wires and plugs is the way to go sometimes,,, good luck   Aaron kf4eyr
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K5LXP
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« Reply #10 on: February 04, 2003, 11:03:28 AM »

Hi Everyone;

It's been a while since I've rechecked this thread, I hope you haven't given up yet.

The thing about interference such as this is there's usually just one thing that makes the big difference, you just haven't stumbled on it yet.  And sometimes, merely 'shotgunning' the vehicle with ground braids and ferrites is easier than meticulous investigation and trial and error.  On an old grand marquis I had, the fuel pump noise was about S7, with a bit of ignition noise along with it.  That car I didn't even bother sniffing, I just made up a dozen braid straps and with some self tapping screws and star washers, went ahead and bonded every body panel to the frame.  The Ford fuel pump noise problem is well known, so I cut the wires to the pump near the tank, soldered capacitors across the leads and ran a ground from there to the frame too.  Right off the noise went down to S2-3, which the noise blanker took care of. That's 24dB or so of suppression, which is pretty significant.  Might've even gotten more if I worked under the hood some more.  Bottom line is that sometimes it's quicker and easier to just ground and bond everything, instead of surgically trying to find the worst offender.

The earlier post about resistor wires and plugs is quite valid, per a post I just made yesterday over in the Elmer's forum I had an '85 Chevy S-10 that was S-9 ignition noise.  Just by changing the wires to resistor type virtually eliminated it.  Also, $130 for shielded wires doesn't sound that expensive to me, a decent set of non-shielded silicone resistor wires will run you over half that.  We're not talking your basic set of Pep Boys made-in-china wires here.  If you try to put a value like that on your ham radio activities, it'd be cheaper for all of us just to call each other on the telephone.  All the money and time I spend on my ham radio activities has provided me not only with an engaging, lifelong, and satisfying hobby, radio is my livelihood as well.  (though sometimes it's hard to convince the XYL of that...)

Mark K5LXP
Albuquerque, NM
k5lxp@arrl.net
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N1MXB
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Posts: 5




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« Reply #11 on: February 04, 2003, 11:18:45 AM »

I have a tacoma 2001, grounding the pipe and the body parts solved 95% of the problem, use cooper shield r8 straps  and you will see the difference.
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KB7TEF
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Posts: 16




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« Reply #12 on: February 05, 2003, 03:38:13 PM »

Hi Mark and everyone.

Well, here is an update on what I have done.  Saturday I spent the day grounding.  I used 1/2" braided strap and grounded the hood, doors, tailpipe, bumper, and each side of the body to the frame.  Before grounding I had about s9 of noise and the Noise Blanker did nothing.  Now I get about s7 of noise and the NB takes it to about S4.  Substantially better than the S9, but still not where it needs to be. I have decided to invest in the Magnecor cables to see if they do the job.  Something tells me that the existing noise is still coming from them.  Hate to spend the money, but there is no use having a nice mobile setup if you can't use it to its fullest Smiley.

The noise I still hear is definitely ignition noise, and sniffing under the hood I hear the exact same noie from the cables.  

This group has been great!  I surely appreciate all the advice and kind words.  I was about ready to give up hope.  I will post and let you know how the Magnecor wires work, and if they are worth the cost.

KB7TEF
Steve
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KB7TEF
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« Reply #13 on: February 05, 2003, 03:40:57 PM »

Oh yeah, one thing I did learn. Don't touch spark plug wires that have been shielded with aluminum foil unless it is well grounded  Smiley

Steve
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K6TFZ
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« Reply #14 on: February 13, 2003, 06:12:48 PM »

There was an article in QEX early last year applicable to a 4Runner. Braided shield with caps on the spark plugs to start, completely shield the distributor cap, bypass caps and chokes on the fuel pump. Find the article. It appeared not easy and very scientific but it worked (I believe it was a ham down in San Diego.).
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