Author Topic: plug wires  (Read 3875 times)

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390owner

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plug wires
« on: December 08, 2024, 09:24:39 AM »
I had a miss with my 390 pulling a hill. So I opened the hood after dark with it idling and had blue fire around the 4 front plug wires One of them was arcing  from the plug to the distributor. So I bought a new set of ford racing wires. They are doing the same thing. I put a small amount of grease inside the wire boots. What am I missing?

gregb

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Re: plug wires
« Reply #1 on: December 08, 2024, 11:04:49 AM »
I'd change the cap too.....how old are the plugs?

390owner

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Re: plug wires
« Reply #2 on: December 08, 2024, 07:27:11 PM »
I have an hei distributor and the plugs arent that old maybe 5000 miles

TJ

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Re: plug wires
« Reply #3 on: December 09, 2024, 08:56:39 AM »
Before spending anymore money, look at the plugs...even though they're relatively new.  Also, clean the contacts inside the cap if it hasn't been done in a year or more.  At the least, pull it off and look inside.

Also, even though your wires are new, they may have been damaged if you pulled them off the plugs by hand.  Some wires can tolerate being pulled off the plug by grabbing the boot.  Some wires break apart inside if you don't use plug wire pullers.

Electricity can be like water.  If it can't go where it's supposed to go, it goes someplace else.
« Last Edit: December 09, 2024, 09:07:35 AM by TJ »

GerryP

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Re: plug wires
« Reply #4 on: December 09, 2024, 12:08:45 PM »
The corona around the spark plugs is just physics.  Under the right atmospheric conditions and, of course, darkness, you will see this corona even with new wires.  The arcing is something that needs to be addressed.  There is resistance higher than the intended path can handle.  It could be a spark plug gap too wide, a fouled plug, a carbon tracked cap, the wire terminal not seated into the cap and all that.

Thumperbird

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Re: plug wires
« Reply #5 on: December 09, 2024, 12:22:53 PM »
Probably not it but a quick check for a good engine ground?

MrRupp

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Re: plug wires
« Reply #6 on: December 09, 2024, 05:34:16 PM »
I was always taught that electricity is lazy, and it will find they easiest path. Sound like to me is you have a carbon track in the distributor cap. Just a guess.

390owner

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Re: plug wires
« Reply #7 on: December 10, 2024, 07:28:11 AM »
Thanks for all the replies. I will check the cap and the plugs

fryedaddy

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Re: plug wires
« Reply #8 on: December 10, 2024, 08:28:19 AM »
i went through the same thing.i replaced everything,changed the plugs last and thats what it was!
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390owner

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Re: plug wires
« Reply #9 on: December 10, 2024, 06:43:20 PM »
The rotor had a little bit of arcing marks on the inside tabs and the rotor end looks a little worn. May just replace the plugs and the rotor and  cap

390owner

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Re: plug wires
« Reply #10 on: December 11, 2024, 06:36:24 PM »
Ordered a new cap and rotor bug. What plugs are you guys using. I have autolite 45 now

gregb

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Re: plug wires
« Reply #11 on: December 14, 2024, 10:16:53 AM »
Autolite 45 is what I use.....

390owner

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Re: plug wires
« Reply #12 on: December 27, 2024, 07:52:27 PM »
New cap rotor, plug wires and it is still arcing Plugs are next

Faron

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Re: plug wires
« Reply #13 on: December 29, 2024, 02:23:28 AM »
Plugs should of been First , given the Ifo provided , I also disagree with All wires will have the Plasma display , if the do they are leaking energy , and yes electricity is lazy easiest path to ground , and speaking of GROUNDS , to many combos with poor Engine Grounding , when in doubt add another !

390owner

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Re: plug wires
« Reply #14 on: December 30, 2024, 07:41:28 AM »
Over the years on my trucks I have owned every time this happened it was the wires. That is why I changed them first. The plugs are on order so the worst thing is I have a new rotor, cap, wires, and plugs. I enjoy asking questions here to get your opinion. Sometimes you guys are right on the  problem other times your not. Thanks for all the responses

390owner

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Re: plug wires
« Reply #15 on: January 11, 2025, 06:24:06 PM »
Still has the miss at a hard pull. New plugs, wires, rotor, and cap. The engine is grounded to the frame and the radiator support and battery. What else could this be?

Thumperbird

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Re: plug wires
« Reply #16 on: January 12, 2025, 07:58:44 AM »
Coil?

CaptCobrajet

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Re: plug wires
« Reply #17 on: January 12, 2025, 01:36:34 PM »
Might be a burnt valve if it only does it under load.  Easy test…….Get it to operating temp, and shut it down.  Take the coil wire off so it won’t start up.  Spin it over and pay close attention to the sound.  Does it skip or speed up as it makes a round or do all of the cylinders sound consistent?  If you have a skip, then check cranking compression to see which one.  If it isn’t up top, it is probably an exhaust valve leaking.
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My427stang

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Re: plug wires
« Reply #18 on: January 15, 2025, 12:42:57 PM »
If you haven't found anything, consider trying it with vac advance unhooked.  I have seen Ford distributors with bad wiring make and break contact or short as the vacuum advance comes in.  Unhooking it, usually runs ok, then see what's going on. 
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390owner

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Re: plug wires
« Reply #19 on: January 15, 2025, 07:51:59 PM »
I ordered a coil but have not received it yet. Good Idea to try if coil does not work

galaxiex

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Re: plug wires
« Reply #20 on: January 15, 2025, 09:11:22 PM »
If you haven't found anything, consider trying it with vac advance unhooked.  I have seen Ford distributors with bad wiring make and break contact or short as the vacuum advance comes in.  Unhooking it, usually runs ok, then see what's going on. 

This ^^^ was VERY common on the GM HEI in the late 70's early to mid 80's.
GM used rather stiff and "not" very flexible wire on the module in the dist.

I didn't think it was very common on Fords... at least I never encountered it.
Not saying it couldn't happen, just not common.


GM got smarter and started using much better quality, high strand count flexible wire at some point.
Every 20 minute job is 1 broken bolt away from becoming a 3 day ordeal.

shady

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Re: plug wires
« Reply #21 on: January 16, 2025, 09:24:48 AM »
Most fords use a resistor wire from the ignition switch to the positive side of the coil that I've had go bad. Make sure that you have the proper voltage on the coil. Also make sure the coil isn't connected backwards ( - side goes to the points). Lastly don't overlook a bad ignition switch. You can always hot wire 12v to the + side of the coil and see if that fixes the miss, but it will be hard on the points so you might want to put an old set in to try.
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390owner

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Re: plug wires
« Reply #22 on: January 20, 2025, 08:25:09 AM »
Replaced the coil did not make any difference. I have a hei dist.  so no points Thanks for all the replies