[AJD] sparkplugs- problem - failures - maintenance - new technology

[Duane Larson]

Kreig,
I'll take a shot at your questions, but keep in mind spark plug discussions 
are a first cousin to religion and politics discussions.
1) Why do plugs go bad?  A bad plug normally means one which will not 
produce a spark to ignite a gas/air mixture.  This can be due to several 
reasons, including 1) a cracked or broken porcelain but more commonly 2) an 
insulating covering of combustion products interfering with production of 
the spark at the plug gap, 3) a wrong size gap, ..... .  In a functional 
plug the spark is supposed to occur between the center electrode and the 
ground strap, but will occur at the point of least resistance and that is 
not always at the gap particularly if there are cracks in the insulator. 
Modern plugs tend to "go bad" more frequently than plugs manufactured when 
our tractors were built because back then the insulating porcelain around 
the center wire at the gap was glazed to inhibit absorption of combustion 
products in the porcelain - which if that happens reduces the insulating 
properties of the porcelain and allows the spark to occur elsewhere than at 
the gap.  Glazing was an extra step which cost money, and as the fuel 
control in automobiles became stricter, flooding of engines became unusual 
and glazing was basically eliminated.  However, our tractors tend to run 
rich (partly as a result of getting them to idle down) and that results in 
the porcelain absorbing the combustion products (including oil from 
less-than-ideal engine condition).  Besides less than optimum spark plugs, 
other components of the ignition system can cause problems, including use of 
carbon-core plug wires (copper core wires should be used), corroded 
connections at the plug wires, and having the coil connected backwards in a 
distributor ignition system.  These can be easily corrected.

2) I don't know that plugs go bad in Deere's more often than other 
tractors - I don't think the plug knows where it is located so it would be 
the matters discussed in 1) (running rich, other electrical issues) in 
addition to the matter of often depending on a thermosyphon system to bring 
the engine to operating temperature.  Most other brands use a 
thermostat/water pump system and can more easily cause the engine to run at 
an optimum temperature and burn off combustion products.  I have a 1950 VAC 
Case which is my working tractor and I don't remember the last time I 
changed plugs in it, but it runs about 180 degrees when working.  Use of 
antifreeze also reduces effectiveness of the thermosyphon system, and often 
shutters don't work or aren't used and our Deeres don't work hard enough to 
come up to 180-190 deg.  I always use the hottest spark plug I can find in 
my Deeres, unless heading out to plow or other "serious" work - then I 
change to a cooler plug.  It is REALLY rare to pull a plug from a Deere and 
observe symptoms of a "burned" plug!!

3) Preventive maintenance - I would extend to the electrical system and 
cooling system - includes removing, inspecting, and cleaning plugs.  If you 
are using plugs which have glazed "noses", DO NOT use abrasive cleaners on 
them - carb cleaner with a plastic scrub pad will get them back to like new. 
Abrasive cleaners damage the glaze.  I don't worry too much about the crush 
washers as our tractors are low enough compression that I only replace them 
when they have NO "crush" left.  Functional shutters, clean cooling system, 
proper plug wires and removal of corrosion are all important maintenance 
features, as well as satisfying yourself that your temperature gauge/sensor 
is working.

4) Modern technology - is for modern technology - I see no advantage unless 
someone is back to glazing noses again and I doubt that is the case. 
Speaking as a plug collector there are no new ideas in plugs that I have 
seen.  My solution to the plug matter is to run two-piece take apart plugs 
like came in our tractors (for example, Champion 2ComL 7/8" plugs were made 
into 1961 when they were replaced by the one-piece W18).  My GPs mostly 
parade but sometimes plow, and I take them apart, clean the porcelain, and 
reassemble (takes about 5 min/plug) - and presto, I have new plugs.  I have 
had the same set in my '31 GP now since1994 and they work fine.  The problem 
is they cost $15-$20 apiece now and folks don't seem to want to pay that 
much for a plug.  Modern technology has given us resistor plugs which are 
necessary for modern automobiles but bad stuff for old tractors.  The 
Autolite 386 and 388 18mm plugs are favored by collectors but they are both 
resistor plugs - I would use the Autolite 3116 - about the same heat range 
but non-resistor.  I haven't used any of the "tricks" like plug extenders, 
long reach modern plugs with adapters, etc., for the reasons mentioned above 
so can't comment on those.  I don't think AC-Delco is making many plugs 
anymore, so Champion and Autolite (and Stitt if you want a REAL expensive 
plug) are the "US" brands left.

Sorry for the length - this may not even go through.  I'm sure others will 
have other opinions.

Regards,
Duane Larson

----- Original Message ----- 
From: <astroguy at nas.com>
To: <antique-johndeere at lists.antique-tractor.com>
Sent: Thursday, November 16, 2006 9:52 PM
Subject: [AJD] sparkplugs- problem - failures - maintenance - new technology


> Seems like a lot of problems with JD tractors, comes from troublesome
> sparkplugs.
>
> So my questions are:
>
> 1)     Why do spark plugs go bad?
>
> 2)     Why do spark plugs go bad so fast in JD tractors?
>
> 3)     Is there a way to do some kind of preventive maintenance for plugs?
>
> 4)     Are there new technology sparkplugs that eliminate the need to
> purchaseng new plugs ever year? Bosche now produces Platinum Ir Fusion
> plugs made up of platinum and Iridium.  Reading the literature, sounds 
> like
> a great spark plug.
>
> Any thoughts??
>
> Thanks, Kreig
>
>
>
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