Spark is arcing!

N

newtong_ware

Seaman
Joined
Sep 18, 2005
Messages
59
I am having an issue with the #4 cylinder plug arcing from beneath the boot to the outside of the spark plug.

I have tried the dielectric grease and tried it dry. I even pulled a boot from a different coil and tried that. I thought I had it, but no, still arcing out.

This is really a pain and I am pretty darn good on electrical and electronics and this is really puzzling me.

Am I missing something basic here?

This is a 1976 Johnson 115 etl. Newly rebuilt engine. New coil. When it don't arc, it purrs, then it starts arcing and the rpms drop and all of that bad stuff.

Any ideas?

>>>>Newt
 
HighTrim

HighTrim

Supreme Mariner
Joined
Jun 21, 2007
Messages
10,486
Re: Spark is arcing!

Which coil kit did you use?

Did it come with new wires?

Age and condition of plugs? Cracked ceramics? Carboned?

The spark is travelling the path of least resistance.
 
E

ezeke

Supreme Mariner
Joined
Sep 19, 2003
Messages
12,532
Re: Spark is arcing!

Yes "The spark is travelling the path of least resistance."

Carbon, possible bad connection from boot to wire, or cracked ceramic insulator.

Any chance you have a spark plug in a heli-coil?


Try running a grounding strap from the ignition coil rack to the problem cylinder head - you should already have one to the starboard cylinder head.
 
jay_merrill

jay_merrill

Vice Admiral
Joined
Dec 5, 2007
Messages
5,653
Re: Spark is arcing!

Make sure that the ceramic portion of the plug is absolutely clean. If there is any black "soot" on the plug at all, you may be getting carbon trail arcing.

You may also wish to lose the OMC spark plug wires and use automotive type wires with the spark plug boot factory installed. I did that with my 1972 Johnson 65hp for the same reason. Many auto parts stores sell generic plug wires with boots on either end. I bought two for five bucks each, cut them in the middle and used three of the resulting four wires. I no longer have problems with the wire/clip assembly coming loose inside of the boot, etc.
 
HighTrim

HighTrim

Supreme Mariner
Joined
Jun 21, 2007
Messages
10,486
Re: Spark is arcing!

Be careful with the type of wire though!

Have never personally had any trouble with OEM wire/coils/boots, but have heard that the NGK motorcylce boots are a good replacement. This is not from personal experience however, simply word of mouth.
 
Lakester

Lakester

Chief Petty Officer
Joined
Nov 17, 2007
Messages
428
Re: Spark is arcing!

newtong_ware said:
Any ideas?

>>>>Newt
Click to expand...

hello,

ideas? :D always have an idea... :p

well i have seen plugs arc to outside grounds. raising the wire connection to the plug 3/8" stopped it in that case...

and if it were mine, i would definitely try a strong nylon tye strap or two around the boot to insulator connection. the "path of least resistance" may not be that... well defined. and this may direct the voltage thru the plug to its gap... by disrupting the path of least...

let us know what u try and results.

regards
lakester :cool:
 
iwombat

iwombat

Captain
Joined
Jul 12, 2006
Messages
3,767
Re: Spark is arcing!

My guess is that your spring-clip is no longer making good contact with the wire. You might try cutting your plug wire back another 1/4" and re-inserting the spring clip and boot. On a good working plug wire and plug the boot isn't even necessary. Heck, 30's motorcycles had just a ring-terminal and a screw-tip plug.
 
1

-1boat

Seaman Apprentice
Joined
Feb 23, 2008
Messages
38
Re: Spark is arcing!

I'll bet you have a cracked plug insulator. Swap the questionable plug to a different cyl. and see if the problem also moves.
 
N

newtong_ware

Seaman
Joined
Sep 18, 2005
Messages
59
Re: Spark is arcing!

Allright guys, lot's of thoughts and I can see a bit more info is called for.

I really think it is a wire issue based on your responses.

It is a new Sierra Coil (less than 20 hours), new plugs, and no helicoil. I have cut back and re-set the wire clip.

I have swapped plugs and tried the boot off of the old coil and the problem stays at the #4 spot.

I like the idea of an additional ground on that head, and the new wire/ boot assembly. I have an old Harley I work on when I get tired of working on my old boat. I probably have some decent plug wire/boots I can put on that coil from an upgrade I did on the sooter. My question is how do I attach the new lead to the coil without cutting up something that shouldn't be cut? I haven't looked super close yet, but I thought that was pretty sealed up.

Thanks,
Newt
 
iwombat

iwombat

Captain
Joined
Jul 12, 2006
Messages
3,767
Re: Spark is arcing!

How did you set the wire clip?

Very important to do it by the book.
 
C

CharlieB

Vice Admiral
Joined
Apr 10, 2007
Messages
5,617
Re: Spark is arcing!

Throw that boot away!!!!!!

You could try testing without the boot, but WOT in gear is the only true test.

The boot has a carbon track burnt into it, replace the boot.

You already proven the plug OK by switching plug and the problem remains at #4 (with the BOOT).


Marine plug wires are usually multistrand stainless core

Automotive wires are usually carbonized thread, NOT a good choice for the marine application.
 
C

CharlieB

Vice Admiral
Joined
Apr 10, 2007
Messages
5,617
Re: Spark is arcing!

Re-read all posts and noticed that you stated that you DID try another boot, problem remained unchanged. hmmmmmmmmmmm

Looking

What Sierra coil did you install?

I haven't looked up your model yet

Single coil or multi coils
If multi try switching the coil with another, see if the problem follows.

I'm beginning to suspect it may be the incorrect coil for your ignition.
 
C

CharlieB

Vice Admiral
Joined
Apr 10, 2007
Messages
5,617
Re: Spark is arcing!

Unless I looked it up wrong, your coil should be

J/E 0502890
Sierra 18-5194
CDI 183-4632

Retest the coil on another cylinder, if the problem follows the coil then it's time for a phone call to Sierra Tech, hopefully they will agree to replace the coil.
 
E

ezeke

Supreme Mariner
Joined
Sep 19, 2003
Messages
12,532
Re: Spark is arcing!

If it were the coil, it would arc at the coil. Your problem is either at the spark plug end, or you are not using solid core wires.
 
MikDee

MikDee

Banned
Joined
Jun 6, 2007
Messages
4,745
Re: Spark is arcing!

I've had issues like this in the past, and the only thing that has worked for me is either to use a Resistor plug, with any type metal stranded spark plug wires, Or, a non-resistor plug with suppression (resistor) wires. good luck, Mike
 
N

newtong_ware

Seaman
Joined
Sep 18, 2005
Messages
59
Re: Spark is arcing!

Guys,
Wierd stuff. I took a look at the offending coil, just to see how the wire was connected to the coil, gave it a little wiggle, and it just came out. Looks like they were just pushed in and a little sealer dribbled over them. The others look ok.

Yesterday and today, after making sure that the coil and wire were correctly fitted, and with a little electrical tape in a can over the connection, the engine has done something it has never done before... it turned over about twice, and fired right up. WOW!

I spent 13 years working on copiers, and I know high voltage does strange things, but I can't figure how this works, unless it is a result of an air gap/ high impedence thing. I wonder if it could have been effecting anything other than this one cylinder. It is hard to believe one plug acting up can make that big of a difference in the overall operation of the engine.

Any words of wisdom??

Thanks to all.
Newt
 
You must log in or register to reply here.
Top