spark plug cap resistance

tew45 · 11-08-2007, 11:07 PM

My Yamaha G9 plug cap opens and has no resistance (does not run then). The manual states it requires 5K to 6K ohms to work. Why does it have to have 5K to 6K ohms and not a direct connection?

spriddle · 11-09-2007, 08:57 AM

I'm not what your asking here. Most NGK plugs (if that is what you are using) are pre gapped. If your having spark issues, maybe you have a problem with your coil or air/fuel mixture causing it to fowl out. If your wanting more spark, try using one of the new NGK Irridium plugs.

tew45 · 11-09-2007, 09:37 AM

It is not the spark plug, it is the cap that attaches to the plug. If you remove the cap and measure the resistance from where the plug top fits to where the wire fits in the resistance is around 6K ohms. It is there to get a better spark, current limiting, noise reduction or to protect the coil or ignition circuit. My cap has opened two times and will not pass a spark. I want to know if the circuit will work without damaging something by eliminating the cap and running the wire direct to the plug. Sorry about being vague but it was late last night and I didn't know how to state the problem.

spriddle · 11-09-2007, 09:47 AM

If I read this right (I appologize if not), your plug CAP has cracked/split a couple of times. I've seen this on Yamaha's before. I'm not sure if it is caused by overloaded spark or simply heat. You definitely need to use the cap (for insulation). If not, the spark is going to arc and ground out on the top of the engine. The simplest thing to do (since it sounds like the spark is normal) is just wrap some electrical tape around the cap where it is cracked and forget about it. I had to do this on my old G9 and it worked fine for years.

tew45 · 11-09-2007, 11:20 AM

Not there yet! The cap is almost new and is in perfect outside condition but it has an internal resistance of around 6K ohms. When this resistance disappears the spark will not pass from the wire to the plug. My cap's resistance has disappeared two times now and I need to know why the resistance is necessary or I would like to know before I have to keep buying plug caps!

spriddle · 11-09-2007, 02:03 PM

I don't know the answer to this question. I would say maybe a bad coil or ignition module. I would start with the coil.

TheNewGuy · 11-09-2007, 02:44 PM

Big Block it...no more problems!!

spriddle · 11-09-2007, 03:07 PM

Quote:

Originally Posted by TheNewGuy

Big Block it...no more problems!!

That's what I'm talkin about!!

tungpo1 · 11-09-2007, 04:08 PM

I agree just pop one of these in!!!!!!!!!!!!!!!!

11-08-2007, 11:07 PM	#1
tew45 Gone Wild Join Date: Aug 2007 Location: North Texas Posts: 2,312	spark plug cap resistance My Yamaha G9 plug cap opens and has no resistance (does not run then). The manual states it requires 5K to 6K ohms to work. Why does it have to have 5K to 6K ohms and not a direct connection?

11-09-2007, 08:57 AM	#2
spriddle Admin Join Date: Dec 2006 Location: TN Posts: 101,856	Re: spark plug cap resistance I'm not what your asking here. Most NGK plugs (if that is what you are using) are pre gapped. If your having spark issues, maybe you have a problem with your coil or air/fuel mixture causing it to fowl out. If your wanting more spark, try using one of the new NGK Irridium plugs.

11-09-2007, 09:37 AM	#3
tew45 Gone Wild Join Date: Aug 2007 Location: North Texas Posts: 2,312	Re: spark plug cap resistance It is not the spark plug, it is the cap that attaches to the plug. If you remove the cap and measure the resistance from where the plug top fits to where the wire fits in the resistance is around 6K ohms. It is there to get a better spark, current limiting, noise reduction or to protect the coil or ignition circuit. My cap has opened two times and will not pass a spark. I want to know if the circuit will work without damaging something by eliminating the cap and running the wire direct to the plug. Sorry about being vague but it was late last night and I didn't know how to state the problem.

11-09-2007, 09:47 AM	#4
spriddle Admin Join Date: Dec 2006 Location: TN Posts: 101,856	Re: spark plug cap resistance If I read this right (I appologize if not), your plug CAP has cracked/split a couple of times. I've seen this on Yamaha's before. I'm not sure if it is caused by overloaded spark or simply heat. You definitely need to use the cap (for insulation). If not, the spark is going to arc and ground out on the top of the engine. The simplest thing to do (since it sounds like the spark is normal) is just wrap some electrical tape around the cap where it is cracked and forget about it. I had to do this on my old G9 and it worked fine for years.

11-09-2007, 11:20 AM	#5
tew45 Gone Wild Join Date: Aug 2007 Location: North Texas Posts: 2,312	Re: spark plug cap resistance Not there yet! The cap is almost new and is in perfect outside condition but it has an internal resistance of around 6K ohms. When this resistance disappears the spark will not pass from the wire to the plug. My cap's resistance has disappeared two times now and I need to know why the resistance is necessary or I would like to know before I have to keep buying plug caps!

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11-09-2007, 02:03 PM	#6
spriddle Admin Join Date: Dec 2006 Location: TN Posts: 101,856	Re: spark plug cap resistance I don't know the answer to this question. I would say maybe a bad coil or ignition module. I would start with the coil.

11-09-2007, 02:44 PM	#7
TheNewGuy Admin/Moderator Join Date: Dec 2006 Location: Ohio Posts: 18,046	Re: spark plug cap resistance Big Block it...no more problems!!
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11-09-2007, 04:08 PM	#9
tungpo1 Gone Wild Join Date: Dec 2006 Location: St. Johns /Jacksonville Posts: 2,383	Re: spark plug cap resistance I agree just pop one of these in!!!!!!!!!!!!!!!!

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