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Ford 9N, 2N & 8N Discussion Forum

spark plug wires

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seemo AR

06-16-2004 21:48:01

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I have an odd problem on a 9N. The Plug on the #1 cylinder will not fire unless there is a gap between the plug and the plug wire. The cylinder has low compression, around 65 lbs. Even with the low compression it will run fairly well if the gap is there. It does not have solid copper wires.

I think I have heard of this happening before but I can't remember the cause.

Thank you for your help.

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Dell (WA)

06-16-2004 23:46:38

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 Re: spark plug wires in reply to seemo AR, 06-16-2004 21:48:01  
seemo..... ...yer really askin' fer itt ain'cha? You already know what part of your problem is, don't cha? low compression. N-Ford specs: 90psi min (dry) and yer reporting 65 psi.

2nd, you really should be using coppercore sparkie wires, and you know that too. Modern anti-radiostatic carboncore sparkie wires cut down on yer sparkie volts ...but... interesting enuff, that extra air-gap that you are providing actually raises the sparkie volts for a hotter sparkie to jump yer BAD SPARKIE.

Bottom line, don't be so cheap. Gitta new set of copper-core sparkie wires and make certain yer using hot AutoLite AL-437 sparkies. And you'll limppa long on 3-1/2 cylinders and 15hp..... ...respectfully, Dell

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06-17-2004 08:11:23

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 Re: Re: spark plug wires in reply to Dell (WA), 06-16-2004 23:46:38  
Dell, I have used the spark gap trick to keep a bad cylinder from fouling the plug for years.

My question is. Do you think that this can contribute to early points failure? Does this make the points have to carry more voltage than normal so as to overload the condenser and not have enough capaticiance to retard the spark at the points?

If it didn't then I have been thinking of cutting the conductor off some on my old TO 20 Ferguson rotor to make it have a larger gap to jump so as to help elimiate fouled plugs and not have to have that sorta dangerous unprotected spark out there in the inviroment where it could cause a fire?????

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Dell (WA)

06-17-2004 13:45:58

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 Re: Re: Re: spark plug wires in reply to ZANE, 06-17-2004 08:11:23  
Zane..... ..every time yer sparkies haffta jump an "extra" airgap, ya loose some of the KILOVOLTS. Which is why you want your rotor gap inside the cap to be a narrow as you can gittitt without it hittin' ennythang. (so you have more sparkies for the plug gap) This is something you can "see" on one of those big TV screen sparkie machines at those fancy tune-up places.

The trick about the "air-gap" for jumping fouled sparkies has to do with "rise-time" of the sparkie pulse. The extra air-gap increases the sparkie rise-time and causes it to jump the sparkie gap rather than leak off the side of the fouled ceramic insulator 'cuz it don't have the time to leak. And as long as you have "excess sparkies volts" yer ok.

Remember the shadetree mechanic's test for sparkies is the ability to jump 3/16" air-gap. Inside the engine under compression, once the sparkie volt pulse reaches the "ionization potential", its gonnna jump the sparkie gap. And any excess sparkie volts just go with the flow across the gap.

Remember, yer sparkie system is designed with EXTRA SPARKIES to allow for normal wear and deteriation. Every 0.001" extra sparkie gap costs about 1-KILOVOLT extra sparkies to jump the gap. (which is one reason to keep yer sparkies gap checked for N's = 0.025")

The normal "arcing" of the ignition points as they open, causes surface resistance to be generated which is one reason you need to replace yer points every so often, because the points resistance reduces the coil AMPS and the magnetic field that collapses to enduce the secondary SPARKIES.

Your condenser is there to suppress that points-arc, but it can't completely. Yer always gonna get a points-arc when they open. And NO, the extra sparkie air-gap that you intentionally introduce to jump fouled sparkies doesn't really effect points wear, it just reduces the available sparkie volts to jump the real sparkie gap.

Of course, as you know, the ultimate "cure" for fouled sparkies is the dreaded "engine overhaul". (grin)..... ..... Dell

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06-18-2004 06:06:45

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 Re: Re: Re: Re: spark plug wires in reply to Dell (WA), 06-17-2004 13:45:58  
Dell, make me understand your statement that the open air gap reduces the voltage across the plug gap. It would seem to me that it has to increase the voltage in order to make it jump the gap more readily when the plug is fouled?????

And why would not the gap at the end of the rotor if it were exagerted not do the same?????

You may have already told me but it has not sunk into this old head yet!


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06-17-2004 09:55:02

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 Re: Re: Re: spark plug wires in reply to ZANE, 06-17-2004 08:11:23  
Zane -- how do you hold the wire and maintain the gap while driving the tractor. I don't have the need but in thinking about it I wonder if a short piece of plastic tubing the right size could be slipped down over the plug and the sparkplug wire slipped down into it to establish the proper gap. If it would work then that would let you see and adjust the gap, see the spark, and insulate the spark from outside potential problems. What do you think ??

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seemo AR

06-17-2004 19:18:16

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 Re: Re: Re: Re: spark plug wires in reply to Cap-N-ID, 06-17-2004 09:55:02  
To leave an air gap, do not push the plug wire down on the plug very far. The boot will keep it from falling off.

Thank you all for the answers you have given me.

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06-17-2004 09:14:46

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 Re: Re: Re: spark plug wires in reply to ZANE, 06-17-2004 08:11:23  
Zane; Champion used to make spark plugs that had a built in gap in them. I don't remember the designation number, but I remember on the end they had a small hole in them. You could bypass the gap by cutting off a paper clip wire and inserting it into the hole. This was in about 1974. I had to order them then. Check Champions web site, they might still make them. I also heard those plug risers you can buy to put under the plug worked well, but no room on an 8n. I have never used them. But they may work for your tractor. Mike

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06-19-2004 06:29:07

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 Re: Re: Re: Re: spark plug wires in reply to ihmike(n.e.tx), 06-17-2004 09:14:46  
And only slightly OT,....I was at a farm show in the TX panhandle and some 90 year old geezer was thrillin' the young girls and astonishing the guys by holding onto a magneto-driven JD spark plug lead with one hand and holdin' onto the spark plug tip with the other to demonstrate how he used his body to make the connection. The old tractor would first run on only one cyl then on both as he grabbed the spark plug. The young guys kept trying to lure the girls away from him but they all stood around cooing and smiling at him. He loved it. (This was before viagra so I suspect all the attention from the young girls (or the combination of them and the magneto) gave him his last big one!) I admit I've never had the courage to try it.

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