Melting Distributor Cap?

[chaseincats]

Hi guys,

The plastic surround of the center spark coil lead (only) on my distributor cap has melted a bit for the 2nd time.  The car came with an aftermarket ignition box/coil and has run great for years.  Would putting ox-gard in the center terminal help deflect some of the electricity/heat awa y from the plastic surround?  Here's a picture of the melted center terminal (the other terminals don't have this problem).:

Edited January 10, 2021 by chaseincats

[Zed Head]

You might  just have a dirty/poor connection and the resistance is causing heat.  Maybe get a new center wire and a new cap and make sure that the wire is pressed al the way in.  There really shouldn't be much heat generation there.

[240260280]

wow...never saw that before. Is it Made In China wires? Is it arching there?  There is not much current to heat at that point so it is an odd failure.

[SteveJ]

2 hours ago, 240260280 said:

wow...never saw that before. Is it Made In China wires? Is it arching there?  There is not much current to heat at that point so it is an odd failure.

I saw it once before,  13 years ago. A gentleman was selling a 260Z on Craigslist. He dropped the price from $3,200 to $2,500 because it wouldn't run. It took me a while to figure out what was wrong as I was much lower on the curve for diagnostics skills, but I finally pulled the coil wire off the cap and saw pretty much what @chaseincatsfound. The seller got his $2,500, and I got the 260Z.

[dutchzcarguy]

32 minutes ago, SteveJ said:

not much current to heat at that point

Not much indeed.. few milli amps but very high voltage.. so P=U x I  gets still a few Watts to burn into the plastic cap.. 😉

[240260280]

I'm thinking I^2 * R.  Charge just builds up on the coil to rotor button section then jumps. That plug-wire to cap contact is huge compared to the small button touch point so it is difficult to see how it could be so resistive there.

The connection must be very corroded to heat up and melt plug wire?  I don't get it. 

Edited January 11, 2021 by 240260280

[Racer X]

15 hours ago, chaseincats said:

Hi guys,

The plastic surround of the center spark coil lead (only) on my distributor cap has melted a bit for the 2nd time.  The car came with an aftermarket ignition box/coil and has run great for years.  Would putting ox-gard in the center terminal help deflect some of the electricity/heat awa y from the plastic surround?  Here's a picture of the melted center terminal (the other terminals don't have this problem).:

Where is the boot for the coil wire?

[chaseincats]

Let me try and bulk answer the questions here haha:

- I'm assuming the cap is made in china as it's from my local parts store but the wires are NGK

- The cap and wires are all about a year old and not corroded at all which is the strange part.  This was the case with my old cap and wires and I got the same result.

- The odd thing is the car runs great with the cap/wires as-is

- The boot for the center wire is pulled up for the same of the picture

[240260280]

It seems the wire is heating near the top of the black end that is melting. 

You may be able to use a thermo-gun to measure the temp of the wire at that point and also at the same point but the other end,,,, then reverse the cable to see if a possible higher temperature remains at the distributor end or if it moves to the coil end. This will tell you if the cable or cap is the problem.

[chaseincats]

1 minute ago, 240260280 said:

It seems the wire is heating near the top of the black end that is melting. 

You may be able to use a thermo-gun to measure the temp of the wire at that point and also at the same point but the other end,,,, then reverse the cable to see if a possible higher temperature remains at the distributor end or if it moves to the coil end. This will tell you if the cable or cap is the problem.

Would wrapping electrical tape around the top of the cable's contact help?

[Zed Head]

No.  And if it keeps getting hot the tape will get all melty and gooey.  Big mess.

[chaseincats]

Thoughts on putting some ox-gard in the terminal to draw current away from the plastic?