'50 Chrysler with glowing spark plugs

[Leviathan]

Hello Guys,

Could use your assistance on this one.  The '50 Chrysler was having some slight misfire issues...and tonight I popped the hood while it was dark outside and found that I could see spark, kind of a glowing spark, on each plug wire... which seemed to be originating from under the plug wire cap when it fired. I had cleaned the mating surface of the block where the plugs go in so it was clean and free of debris. I have replaced the plug wires twice...thinking that the first new set was faulty.  The plugs are new (Autolite) and are gapped correctly.  It doesn't idle terribly but does have a slight increase/decrease in rpm's, which I am assuming is due to being able to see spark coming from the plugs at night when the hood is up.  Carb adjustment is correct so it's not that. Any thoughts on correcting this issue would be appreciated!

Thanks.

David

 

[JerseyHarold]

Did you use dielectric grease between the plug wire boots and distributor cap and also between each spark plug and its boot?   You could be getting spark leakage at those points.

[Leviathan]

No. Didn't use d grease. I've not in the past and haven't had issues. I will give that a try and see if it makes a difference. Thanks for the input Jersey!

[squirebill]

Just a consideration.....make certain the metal clip inside the plug wire is clipped onto the metal nipple on the plug.  I replaced plug wires on my daily driver Chevy and the rubber caps were pretty tight and  snapped onto the plug ceramics but I later determined I hadn't pushed them down far enough  to  have the clip of the wire actually clip onto the spark plug nipple.  The dielectric grease on the plug boot made it mush easier to slip onto the plug and get the clip engaged.  Just saying 

[Leviathan]

Thanks for the response Bill. I am taking all of this into consideration and following through. I appreciate it. 

[Sharps40]

If you have a blueish glow along the spark plug wires, they are leaking (bad connections, dirty, deteriorated, wrong type....in any event, the insulation is not keeping the electricity in the core.  Hence, the St Elmo's fire along the wires in the dark.)  The electrical current is travling partly on the exterior of the wires.  Less spark to the plugs and some cross over and misfiring are the results.

Usually the fix is to clean up all the grounds and connections, new cap, rotor, plugs and most expecially, new wires.  i.e. a full tune up should fix the problem and keep the wires from "leaking", arcing.

Edited October 22, 2016 by Sharps40

[55 Fargo]

17 minutes ago, Sharps40 said:

If you have a blueish glow along the spark plug wires, they are leaking (bad connections, dirty, deteriorated, wrong type....in any event, the insulation is not keeping the electricity in the core.  Hence, the St Elmo's fire along the wires in the dark.)  The electrical current is travling partly on the exterior of the wires.  Less spark to the plugs and some cross over and misfiring are the results.

Usually the fix is to clean up all the grounds and connections, new cap, rotor, plugs and most expecially, new wires.  i.e. a full tune up should fix the problem and keep the wires from "leaking", arcing.

I agree, I had my solid core wires glowing on each firing impulse once, this is when I installed and electronic ignition distributor and box, and did not have the correct resistor wires.

[Leviathan]

Actually, the viable spark is only at the boot end...not along the wire itself. I am assuming it is coming from under the boot where it caps the plug. It doesn't make sense that it would be coming from where the plug threads into the head as that should be tight. I am going to wrap the crimped end (Not the tip) with electrical tape and apply d grease to the ends and see if that remedies the situation. Thank you all that responded for your input. Much appreciated!

[Don Coatney]

Electricity always follows the path of least resistance. Are you sure your plugs are set at the correct gap? You might try a different brand of plugs. I use AC DELCO R-45 gapped at .035".

[Dodgeb4ya]

If you are using the factory Chrysler installed Evr- Dry covers do not use the spark plug gasket. It is stated in the MoPar Evr- Dry instruction install kit.

I will have to go out at midnight and start up my 50 Newyorker and see what is going on under my Evr-Dry's!

Anyway some more info...

You might be seeing "corona" which is ionized air that occurs around wires with very high voltage. If you have bad plug wire insulation, you will see a definite spark and you will hear it. Corona will not cause a misfire, but sparking through a weak spot (usually caused by microscopic pinholes in the insulation) will cause a miss since the spark did not occur across the spark plug gap. You might also be seeing "electroluminescence" which is light generated by the spark plug insulator by the short duration high voltage pulse from the distributor. Electroluminescence will not cause a misfire either.

 

[Ricky Luke]

Something else to consider is using cheap wire. I replaced some old carbon core leads on a 1973 Leyland P76 V8 with what I thought were better copper wire leads made from a reel my dad bought at a swap meet . They weren't. It was down on power and hard to start, and at night there was a really good light show. I replaced them with new good quality leads and problem solved! My dad had used the same wire on his 29 Plymouth but he blamed the old coil, plugs, fuel,etc for its poor performance. Getting rid of the rubbish solved the Plymouth's issues.

Rick 

 

[Dodgeb4ya]

Yep ^^^^^ I agree 100%.

A lot of the modern day replacement wire sets for the MoPar flatheads IMO are real poor quality.

I make up all of the ignition wire sets for many old Mopars I work on as I have seen the above issues with replacement wire sets.

I use high quality 7MM  bulk Belden IRS or metallic cable and Snap Lock crimp on spark plug ends. Brass crimp on for the distributor cap.

This requires the proper ignition pliers and a real good stripper.