Spark plugs spark outside of block

Brandon77

Member# 3846
NAXJA Member
Hey Everyone. Hump day!
So i took my Jeep out last night to put some miles on the new gears and lockers and notice all the spark plugs sparking from the outside of the engine. Does this mean i have a bad ground somewhere... maybe block to body ground. Or is this a sign of something else. They are brand new plugs and wires i put in a few months ago. I had a my coil go out recently too and maybe this is the cause of it. Am also getting a low rpm idle now. Any one seen something like this? I am not sure where to start looking for a problem :eyes:.
Thanks
 

Devilfrog

New member
spark leak is usually the sign of bad wires or bad connections ... did you use dielectric grease inside the plug and distributor boots?
Did you get quality wires or just cheapies?
 

sjx40250

New member
Yeah, not a good sign of quality parts. Spark leakage is due to the electricity finding a shorter path than what is intended (spark plugs). Develfrog asked a good question.
 

old_man

NAXJA Member
NAXJA Member
Take the plugs out and clean the ceramic with a good abrasive cleaner. Put on a fresh set of spark plug wires. Don't forget the dialectric grease.
 

Brandon77

Member# 3846
NAXJA Member
spark leak is usually the sign of bad wires or bad connections ... did you use dielectric grease inside the plug and distributor boots?
Did you get quality wires or just cheapies?
Yeah they are the cheap AC Delco 7mm wires and Bosch plugs. I did use dielectric grease but i might of gotten some oil from my fingers on the end of the plugs.


Take the plugs out and clean the ceramic with a good abrasive cleaner. Put on a fresh set of spark plug wires. Don't forget the dialectric grease.
Ok i will pull them out and clean them and re install them with fresh grease while keeping them clean of oil and dirt. I will also swap out the wires for new ones. What brand wires and plugs do you guys use?
 

cruiser54

New member
I'd lose the Bosch plugs for a set of NGKs or Champion Coppers. Use Belden wires available at Napa. Same place you get the plugs.

The grease isn't your issue. That stuff wasn't around for many years and cars ran without sparking between the plugs and wires.
 

N8N_99xj

New member
I've had good luck with Bosch Supers, I consider them equivalent to Champion copper plugs but harder to foul. Bosch Platinums on the other hand... (not on an XJ though)
 

CharlesS

New member
After Champion stopped producing the Truck sparkplug and the stock in the parts system was depleted; I installed a set of the NGK V-Power sparkplugs at the recommendation of the SoCal JEEP guru....
The NGK V-Power spark plugs have worked quite well.....
 

Pelican

NAXJA Member #1191
To each his own -- my 4.0 loves the Bosch Platinums (standard plugs) and I ran the Champion coppers a couple of years to give them a more than fair chance to prove that they are superior. We put all sorts of non-stock stuff that has improved over the years on our Jeeps but for some reason suggest that spark plugs don't fall in that category.

Perhaps I have the only 4.0 XJ in the world that does well on platinum plugs!?!?
 

Brandon77

Member# 3846
NAXJA Member
If the plug gap is too large, what you described will happen. That also might explain why the coil fried.
My coil fried before i installed the new plugs, wires, cap, and rotor. But i think it was doing the sparking before i even installed the new plugs and wires. I do remember airing up the tires at the trail head and hearing a sparking sound coming from the engine just before my coil went out about 50 miles down the road.

I will start with the wires and see what happens. If it still has an issue i will buy some NGK... if it works for you it should work for me. I will post back after. Thanks everyone.
 

cruiser54

New member
My coil fried before i installed the new plugs, wires, cap, and rotor. But i think it was doing the sparking before i even installed the new plugs and wires. I do remember airing up the tires at the trail head and hearing a sparking sound coming from the engine just before my coil went out about 50 miles down the road.

I will start with the wires and see what happens. If it still has an issue i will buy some NGK... if it works for you it should work for me. I will post back after. Thanks everyone.
I'll bet you're gonna be just fine with new wires.
 

5-90

New member
Hey Everyone. Hump day!
So i took my Jeep out last night to put some miles on the new gears and lockers and notice all the spark plugs sparking from the outside of the engine. Does this mean i have a bad ground somewhere... maybe block to body ground. Or is this a sign of something else. They are brand new plugs and wires i put in a few months ago. I had a my coil go out recently too and maybe this is the cause of it. Am also getting a low rpm idle now. Any one seen something like this? I am not sure where to start looking for a problem :eyes:.
Thanks
If it starts on the wire proper, replace the wires.

If it's coming from under the boot on the plug, then remove the wires and clean the inside of the boots and the outside of the plugs.

You can get a dirt or liquid track on the porcelain that will cause HV leakage on the outside of the plug insulator. In fact, it's an old practical joke - you'd remove a couple of plug wires, take a pencil, and shade a heavy line down one side of the plug. Reinstall the wires. Engine would run with a couple of "dead holes" - but the only real potential damage would be that you could burn the plug wires and the carbon tracks from the burned silicone would keep it going after you clean the graphite track off of the plugs (which is why you need to clean/inspect the inside of the boots as well.)

A quicker way to do it would be with a heavy solution of graphite in a light solvent - alcohol usually works. Paint it on with a fine brush - same net result, but less time to get the job done...
 
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