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Coil Sparking to Heater hose

 
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Old 01-16-2019, 09:14 PM
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Coil Sparking to Heater hose

So I noticed my engine miss is being caused by an arc between the coil-to-distributor wire boot right where it passes under the heater hose. The coil is mounted horizontally on top of the intake manifold of the 302. Ignition is Duraspark and coil wire is new!

Anyone have any ideas?

 
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Old 01-17-2019, 07:25 AM
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Originally Posted by jackietreehorn View Post
So I noticed my engine miss is being caused by an arc between the coil-to-distributor wire boot right where it passes under the heater hose. The coil is mounted horizontally on top of the intake manifold of the 302. Ignition is Duraspark and coil wire is new!

Anyone have any ideas?
I'd definitely get another new coil wire and try it. If that doesn't help then I'd reroute the heater hose or move the coil. Voltage should not be leaking like that though, in any case.
 
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Old 01-17-2019, 08:02 AM
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Here is a pic of the trouble spot. Couldnít get the arc to show but about 1/4 blue spark between the boot and hose!
 
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Old 01-17-2019, 11:36 AM
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Electricity always finds the easy route to ground.
It is the whole package from coil to plugs and if you have high resistance anywhere the spark will find ground.
Large plug gap adds resistance.
Dave - - - -
 
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Old 01-17-2019, 12:52 PM
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Plug gaps are normal, .038-.040. Plugs, wires and distributor are new. Cap and rotor low miles but a few years old. Grounds might need some work. Anyone see anything wrong with this placement?

 
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Old 01-17-2019, 09:00 PM
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I don't know if it'll help you out, but I'll show you a couple pics of my setup. It's hard for me to tell exactly what yours is doing with the pic that close up, but I'm guessing our routing is a little different. Mine is a 302/C4 with A/C. The coil wire goes from the coil and loops up and over to the distributor. You can get a pretty clear shot of the coil wire in the first pic hanging in the air by the air cleaner snorkel. The second pic shows you that it's nowhere near anything else. It goes up enough over the top heater hose that you can't see it in that pic, even though it's not the greatest angle. The "wire" in the second pic by the distributor is actually the steel fuel line for the carb and the hose to the left of it that disappears under the A/C bracket is for the vacuum advance on the distributor. Hope that gives you and idea. Good luck, sir.



 
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Old 01-17-2019, 09:05 PM
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Thanks, I'll tinker with it.
 
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Old 01-18-2019, 04:22 AM
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I think I would pull the coil wire back off the coil and look really close at the tip of the coil itself and make sure it isnít cracked or something. Then, if you have a quality coil wire on there the only other thing I can think of is make sure you have a good engine ground.
 
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Old 01-18-2019, 04:29 AM
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Originally Posted by jackietreehorn View Post
...Anyone see anything wrong with this placement?
Yes. For one you should not have anything laying on top of the boot and putting pressure on it. Whether it's rubber or not.
Second, what are those coiled wires doing there? Building up an inductive current? Yeah, I know. A long shot...

But whatever those wires are, they should not be open tipped and coiled around the hose so close to the ignition system.
Now, is this what's causing your trouble? Maybe not. Maybe it's just that the new wires are not up to snuff. We run into this all the time.
Just yesterday someone on another forum had brand new wires with two of them bad right out of the box. So yeah, reasonably new and otherwise perfectly fine wires may have deteriorated to the point that you're getting jumping sparks.

I'd just start by moving the hose (or the coil?) though and see what that gets you.

Paul
 
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Old 01-18-2019, 07:25 AM
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Originally Posted by 1TonBasecamp View Post
Yes. For one you should not have anything laying on top of the boot and putting pressure on it. Whether it's rubber or not.
Second, what are those coiled wires doing there? Building up an inductive current? Yeah, I know. A long shot...

But whatever those wires are, they should not be open tipped and coiled around the hose so close to the ignition system.
Now, is this what's causing your trouble? Maybe not. Maybe it's just that the new wires are not up to snuff. We run into this all the time.
Just yesterday someone on another forum had brand new wires with two of them bad right out of the box. So yeah, reasonably new and otherwise perfectly fine wires may have deteriorated to the point that you're getting jumping sparks.

I'd just start by moving the hose (or the coil?) though and see what that gets you.

Paul
What coiled wires? Where?
 
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Old 01-18-2019, 04:08 PM
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Sorry, I misinterpreted what I was seeing in the image.
The wires showing just behind the hose and the wire-type ring clamp on the hose looked like the same thing. Now that I look more carefully I can see it's just the clamp.

Paul
 
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Old 01-18-2019, 05:28 PM
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Thats a genuine FOMOCO spring clamp! Anyway I moved the coil back a 1/2" as well as moved the coil neg wire off of the heater hose and it seems to be ok.
 
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Old 01-18-2019, 06:26 PM
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Is that a oil field coil laying on its side? Your plug wires also don't have very thick boots which can cause voltage leaks.
 
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Old 01-18-2019, 06:51 PM
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Good point. Is that an original Ford coil jackietreehorn? I don't see the usual yellow-ish top, but don't know if they all had that or not.
The Ford coils were oil-filled too, but apparently were sure that there was no air remaining inside to expose the hot windings to. Aftermarket coils are not quite so diligent in their manufacture anymore it seems.

If it's aftermarket, the usual practice is to find someplace that you can mount the coil at least "mostly" vertical to avoid overheating it.
If it's been in this position for a long time however, I'm guessing (but only guessing!) that you're in good shape and won't have any issues.
But it's still "a thing" to be aware of.

I've been using epoxy-filled coils in other builds where that type of coil shape is still needed. Just so I can avoid any issues with mounting it horizontal.

Paul
 
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Old 01-18-2019, 09:49 PM
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Coil is aftermarket, pulled from an old T-bird in junkyard. Yes the plug wires are skimpy 7mm. Interesting point about epoxy filled canister coils; who makes those?

Arcing has stopped since I moved the coil a little.
 

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