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Engine Spark plug wire corona

  • Thread starter Thread starter Barron91lx
  • Start date Start date Jun 9, 2019
  • Tags Tags
    corona spark plug wires

Barron91lx

Member
Dec 21, 2018
26
3
13
Newton, KS
Jun 9, 2019
#1
  • Jun 9, 2019
  • #1
First of all, thanks to everyone who has helped me work on my car for the last two years.
My 91 5.0 has an unusual problem. Observing the engine running in the dark is a faint light show. Multiple places on the wires are contacting the engine components around them and there is light around every boot. It isn't as bright as a total failure of a plug wire, but it is on every one of them. Interestingly, when I put the coil wire in my hand and move it, the light moves with my fingers. I understand that what I'm seeing is referred to as corona but I don't know why it's happening. I have replaced the wires 3 times in the last year. The advice keeps coming down to new wires. The wires I have on it right now are good ones that I cut to length and they are doing the exact same thing as the others. I grabbed the top of my distributor yesterday and felt a slight jolt where my hand contacted the intake. My distributor is also less than a year old. It's an MSD that I bought new. Could there be something wrong with it? Is it possible for this to occur if the timing is off? I thought it might be the ground so I bought a big ass ground strap that connected to the front ground area and it didn't change. I would try and get it on video but I don't think it's bright enough

Thanks again
 

Dan02gt

mazing how much gas smell came from that tiny hole
20+ Year Stangneter
Mar 2, 2003
909
415
113
Greenville, NC
Jun 10, 2019
#2
  • Jun 10, 2019
  • #2
My car had a wire or two doing this when I got it. The previous owner had installed new auto parts store wires. I replaced them with Motorcraft wires and the problem went away.

Also it seems there have been reliability issues with MSD distributors and TFI modules as of late so if you have a stock one laying around you might want to give it a try.
 
Reactions: Barron91lx

General karthief

wonder how much it would cost to ship you a pair
5 Year Member
Aug 25, 2016
27,842
10,516
203
polk county florida
Jun 10, 2019
#3
  • Jun 10, 2019
  • #3
Your timing has nothing to do with the light show you are seeing.
are the wires hung separate and not touching each other or metal parts? Also used dielectric grease on the boots.
 

Barron91lx

Member
Dec 21, 2018
26
3
13
Newton, KS
Jun 11, 2019
#4
  • Jun 11, 2019
  • #4
General karthief said:
Your timing has nothing to do with the light show you are seeing.
are the wires hung separate and not touching each other or metal parts? Also used dielectric grease on the boots.
Click to expand...
Yes the wires are all in clips and correctly routed. I had dielectric grease on them but I guess I could try adding more.
 

Barron91lx

Member
Dec 21, 2018
26
3
13
Newton, KS
Jun 11, 2019
#5
  • Jun 11, 2019
  • #5
Dan02gt said:
My car had a wire or two doing this when I got it. The previous owner had installed new auto parts store wires. I replaced them with Motorcraft wires and the problem went away.

Also it seems there have been reliability issues with MSD distributors and TFI modules as of late so if you have a stock one laying around you might want to give it a try.
Click to expand...
Thanks. I'll get my old stock dust out and try it.
 

CarMichael Angelo

my rearend will smell so minty fresh,
15 Year Member
Nov 29, 1999
10,641
8,909
234
Birmingham, al
Jun 12, 2019
#6
  • Jun 12, 2019
  • #6
You have replaced your wires three times, but you haven't said what brand they were/are.
Cheap wires are cheap wires...exhaust heat from a header will make quick work of them if they aren't up to the task. If the rest of these 5.0 guys don't have this eerie glow coming from their engines at night, something with yours isn't right.
I've always used Taylor wires on every car I've ever had, ( and I've had a lot). Despite that, I've never felt comfortable putting my hand on any distributor when the car is running..( I don't know what a " slight jolt" is like, but you get zapped by a MSD amplified coil wire, and you won't describe it as slight) It's one thing for spark to be leaking at the boot, but at the distributor on the other end too points right back to bad plug wires. Do not go through the whole process of replacing a coil or distributor, this is an insulation issue. If anything...put a new cap on the distributor that's on it.
 
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