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Spark Plug caps

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Rob Glasgow

Rob Glasgow

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My BT7 developed an engine miss. During trouble shooting the ignition system, I checked the continuity of the HT plug wires. Found 4 of them with a 1.5 to 2.5 Ohm resistance and 2 were completely open, if that is the proper term. Removed the Champion style plug caps (black plastic, 90 degree bend) from the wires and found the caps were the problem. Installed a new set of HT wires/caps and the engine is back to normal.
I replaced the wires with a NAPA set mainly because they were available immediately. (NAPA Part number 700173).
I cracked opened the faulty caps and found the carbon resistor rod was partially eroded. Due to arcing, I think. That would explain the open circuit.
The wire set was replaced 6 years (15,000 miles) ago. The caps did not have a brand name but say Made in England.
I don’t remember seeing this problem reported on the BCF in the past. Am I just lucky? Any ideas what might have caused the caps to fail on two wires but not the other four? I have a Petronix conversion with a negative ground. The new wires do not have a built in resistor, so this shouldn’t be a problem in the future. Just wanted to see if something is going on that I should fix.
 
Hi Rob, thanks for posting. Just wondering if you have a high performance coil installed.
 
I bought a set of those Champion caps already attached to Bumblebee wires and they were absolutely awful. It was impossible to get a good firm fit on the plug. They were made from cheap hard plastic and had very cheap clips inside them one of which broke after about a week. Not sure who actually makes these, I don't think its Champion, but if it isnt how do they get to use the name?
 
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Hi Rob, thanks for posting. Just wondering if you have a high performance coil installed.

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Doesn't make any difference Johnny. These caps have a built in failure mode.Inside the cap is a carbon resistor ,Suppressor, electrical contact beteen the carbon rod and the end electrical connections is via two small round metal disks.It appears that the manufacturing technique can not consistently insure that good electrical contact exists between these individual parts.Consequently, some of them arc iternally and fail as noted herein.---Fwiw---Keoke
 
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I bought a set of those Champion caps already attached to Bumblebee wires and they were absolutely awful. It was impossible to get a good firm fit on the plug. They were made from cheap hard plastic and had very cheap clips inside them one of which broke after about a week. Not sure who actually makes these, I don't think its Champion, but if it isnt how do they get to use the name?

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Just like Lucas parts They pay Champion royalties to use the name.--- /ubbthreads/images/graemlins/yesnod.gif-Keoke

P.S. Use Bosch connctors they do not have any design problems and are available angled or straight. /ubbthreads/images/graemlins/thumbsup.gif
 
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Thats a mistake by Champion - its not doing their image much good - I wonder if they know?

I confirm the internally arcing.

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Image is nothing these days its the bottom line that counts /ubbthreads/images/graemlins/yesnod.gif and I bet you did not send them a notice as to how bad their parts were?. ---Keoke-
 
Just to clarify my comment. I referred to these caps as "Champion style". I got that term from a description in a well know catalog. There was no brand name on the caps, just "Made in England". I doubt if Champion had any thing to do with these particular caps. They are probably just a copy of an old Champion design.
I've been told the carbon resistor in the cap was there to eliminate cross-over induction coming from another wire nearby which might cause the plug to fire at the wrong time. Since the new set does not have resistors built in, can I assume the insulation will do the job by itself.
 
I have a set of six "clip,spark plug, Lucas type" "made in England" that don't work very well, so the vender sent six more that also don't work very well. So I went to Bosch.
 
Hi Rob, I do not know.There are some spark plug wires that have noise suppression built into them. This type can usually be identified using an ohm meter to measure their resistance which should be about 10,000 Ohms. However, if the ones you have are of the conventional stranded copper wire then no noise suppression will be provide by them.---Keoke
 
Hi Rob, thanks for posting. Noise suppresion is only benefitual if you have a radio installed.
Spark plug wires can only induce crossover sparking when the insulation is old and brittle, or when wet. Also, if the wires are routed parallel to each other they may cause this condition. They need to be kept separated. I've never heard of this being a problem on Healey's with four or six cylinders as long as the wires are kept apart.
 
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Hi Rob, thanks for posting. Noise suppresion is only benefitual if you have a radio installed.
Spark plug wires can only induce crossover sparking when the insulation is old and brittle, or when wet. Also, if the wires are routed parallel to each other they may cause this condition. They need to be kept separated. I've never heard of this being a problem on Healey's with four or six cylinders as long as the wires are kept apart.

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That's a rather self centred view isn't it?

Supression reduces rf noise affecting everyone in the vicinity, not just your radio /ubbthreads/images/graemlins/nonono.gif /ubbthreads/images/graemlins/nonono.gif /ubbthreads/images/graemlins/nonono.gif

AWEM
 
No Andrew, not self centered,very few people are aware of the RFI or more correctly Electromagnetic Radiation problems associated with the automobile spark ignition system. Prefering to think its primary purpose is only to protect their own radio equipment These systems lacking proper attention, alteration or design can have severe impacts on adjacent electronic equipment. I recently had a challenging discussion on this same subject with listers in the UK.-Regards---Keoke
 
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