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Spark Plugs

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PA Steve

12-01-2004 12:52:44

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I've been working on an H for the neighbor. I replaced the plugs with autolites, but then the engine started missing severely. In fact, it was only running on two cylinders and sounded just like a JD B.
Anyway, when I pulled the wire off the plug and held it a half inch away from the plug, it fired fine. When I put the wire the whole way on, it started missing again. Then I replaced the plug with an old champion D18Y and it fired with no problem. All plug gaps are correct and point gap is also correct. What causes this? What is the ideal plug for a light/medium duty H?
Thanks,
Steve

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gusc

12-01-2004 22:40:12

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Re: Spark Plugs in reply to PA Steve, 12-01-2004 12:52:44

PA,
The plugs fire when you remove the leads or loosen the leads at the plug because you are increasing the resistance to the plug by making another gap at the lead terminal. This gap is just another form of resistance. Make sure you are using resistor plugs. Increasing the gaps to .035 would probably have made them work.

Plugs and leads must have enough resistance to delay the current flow for a short time to build up the voltage to make a strong spark. Low resistance lets the plug fire too soon with a low voltage weak spark. Works kind of like a condenser but different.

I used Champions for 50 years. Now I won't use them unless it is impossible to get something else, anything but Champions.

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Hermit

12-01-2004 19:04:25

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Re: Spark Plugs in reply to PA Steve, 12-01-2004 12:52:44

Did you, by chance, install Autolite resistor plugs? If your spark was weak and the plug resistance high enough, that would stop the voltage traveling to the plug tip and jumping the gap. When you pull the spark plug wire and hold it away from the plug, it will increase the firing voltage to overcome the resistance. It's a theory anyway.

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John M

12-01-2004 17:50:51

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Re: Spark Plugs in reply to PA Steve, 12-01-2004 12:52:44

They couldnt pay me to waste my money on Champions!They may be ok for like lawnmowers and such,but ALL of my tractors,except for my F14, have Autolite 3116s in them,My recently retired working M has had the same Autolites in in for 9 years now,and havent had a days problem with them.

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12-02-2004 06:42:57

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Re: Spark Plugs in reply to John M, 12-01-2004 17:50:51

I ahve to weight in on this one, I use 100s of plugs a year, this is the split I use and have the best luck with:
Push mowers and lawn/garden tractors- champion

Farm tractors- used Autolite and Champion equally good luck with both

2 cycle chain saws, trimmers, blowers, snow blowers-NGK only, have had brand new snow blowers would not start with Champion, put NGK in and they run great.

could not give me Bosch plugs, have put new ones in and the would not fire out of the box new, put NGK in and they run great.

Now, this is my Opinion and what works best for me. Spark plugs are like snake oil penetrating oils, everyone has the ones they are happiest with.

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retired

12-01-2004 15:41:57

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Re: Spark Plugs in reply to PA Steve, 12-01-2004 12:52:44

Steve If they gave away Autolite plugs I wouldn't use them. I've tryed them on different tractors over the years and always thought they were very short lived, Depending on how you use the H is how to select the plugs, Plowing all day, use Champion D-14 or D=16 Light on and off use the D=18y Parading and a lot of idle time use D=21y Thats my 2 cents worth.

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Mike S 806/H

12-01-2004 13:45:00

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Re: Spark Plugs in reply to PA Steve, 12-01-2004 12:52:44

I use Autolite 3116 and sometimes 386 because I got them Cheep! I recommend 3116

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CNKS

12-01-2004 13:02:59

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Re: Spark Plugs in reply to PA Steve, 12-01-2004 12:52:44

D21 or equivalent--I can never remember the Autolite/AC numbers. There's a weak link in your electrical system somewhere. Could be the wire, coil, or condensor. Other things being equal the old plug could have fired because the gap was wider.

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Dave NE Iowa

12-01-2004 16:11:51

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Re: Spark Plugs in reply to CNKS, 12-01-2004 13:02:59

A old farmer with worn out tractors and little money used to pull the boot off the plug wires to jump the spark --This kind of makes a hotter spark, but I have been told it is hard on a coil. I have done this more times than I can count, just to get a plug cleaned up from oil fouling. I sure do not want to start a issue here on this board but my opinion of the Champion plugs sure differs from the above post. Our local 80 year old mechanic replaces spark plugs 99% of the time before doing anything else, even if you just changed them himself. He insists there is no such thing as quality control in the plug factories. Good luck Dave NE Iowa

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CNKS

12-01-2004 17:56:06

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Re: Spark Plugs in reply to Dave NE Iowa, 12-01-2004 16:11:51

There is a bigger split on Champion vs other plugs than there was with the Bush-Kerry campaign. I am plug neutral. Probably bought more Champions than any other brand, but have had no trouble with any brand. Plugs are cheap. If anyone thinks they are the problem, then change them. Been a lot of plug wars on this forum. I'm not going to participate if this turns into one (even if either of us started it).

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