new spark plugs jumping off 3# spark plug

R

ronford

Member
I have a 1966 Ford Mustang with a 289 code A engine.

After a recent tune up the #3 spart plug wire started backing off the #3spark plug and ultimately jumps off the plug.

A new spark and plug were tightly installed and still do the same. The #3 spark plug wire will still come loose. No other spark plug wires come off only #3.

I know this may be heat caused but why only the #3 plug wire?

Anyone have any experience or suggestions. I have tried to crimp the inside of the spark wire for a tighter fit, but it does not seem to help solve the problem.
Appreciate any thoughts.

ronford, a new member
 
Does that spark plug have the screw on end cap, and is it on the plug, and the wire boot might be swelled.
 
I had a set of wires that did that. I believe the boots were made of some material that "gassed off" when hot and built pressure inside. I finally broke off a piece of toothpick and slid between boot and plug to vent the pressure....no more problem, and after a month or so the wires stayed on without the venting. Yeah...odd. :rolleyes:
Terry
 
To everyone:
I think i have solved my spark plug wire problem. I tried multiple brands of plugs and wires. With normal slip on installation force of the #3 wire on the #3 plug it would not stay on using Motorcraft wires or over the counter wires on an Autolite or on a Motorcraft plug.
Finally, I took the over the counter spark plug wire off the #3 spark plug that was installed on the engine and forced it down on a "spare" spark plug until the rubber boot end of the wire almost touched the metal portion of the spark plug. This stretched the boot and make for a tighter fit. I left the spare spark plug in the rubber boot overnight to allow the fit to set.
Then I installed the stretched #3 spark plug wire on the #3 spark plug (Motorcraft)
and it stayed when the engine warmed up to operating temperature.
Thank each of you for your thoughts on my problem I appreciate it very much.
ronford
 
In my extensive experience with spark plug cables, you always know when the cable-boot is pushed on far enough because you will feel the "click" when the plug wire electrode mates with the groove in the spark-plug electrode.
So, if you could push the boot down further, the plug electrode would be smashing the end of the cable.
I would be concerned with your fix, that it might pop back off due to the pressure being put upon the end of the cable.
 
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