[AT] Firing on two instead of four

[Dudley Rupert]

In line with George's suggestion that you may have a couple of fouled plugs
I am curious as to what the gap is on the "fouled plugs"; that is, is it
less than what the engine/tractor spec calls for?

When we experience a plug that appears to have a good arc when we test it
outside the Head but then when we install it back in the Head and get no
firing it may well be, as George has suggested, a fouled plug that will not
fire when subject to the high pressure of the combustion chamber.

However, I believe there may also be times when we experience this same
scenario that we actually have a "good plug" but one with an inadequate
(i.e., too small) gap.  Remember, the less the plug gap the less is the
voltage that is required to arc the gap.  In this case the arc may look good
to the naked eye (when we test the plug out of the Head) but when the plug
is in the Head there may be insufficient energy in the arc to ignite the
fuel/air mixture.

Just a thought and it may not be applicable in this case.  But, as I say, I
am curious as to what the gap is -

Dudley

-----Original Message-----
From: at-bounces at lists.antique-tractor.com
[mailto:at-bounces at lists.antique-tractor.com]On Behalf Of George Willer
Sent: Saturday, November 25, 2006 6:04 PM
To: 'Antique tractor email discussion group'
Subject: RE: [AT] Firing on two instead of four


Yoda,

Here's your next step... exchange the plugs of the non-running cylinders
with the running ones to see if the trouble follows along.  It may work, I
think it will.

Here's the theory.  Pulling the wire away from the plug forced the coil to
build to a higher voltage before it fires.  That points to a fouled plug
even though they're relatively new.

As you may know, a plug under compression needs higher voltage to fire, so
the test with them laying down outside isn't conclusive.

George Willer

> Hey,
>     I was playing a short time today with my Case SC which I got at the
> end
> of the summer.  It had sat for a few years.  I couldn't get it to fire
> at
> first when I picked it up in August, but just put in four new plugs and
> it
> ran great.
>     Anyway, lately it has been running on just two cylinders.  So I took
> the
> plugs out and cleaned them and laid each individually down and turned
> the
> engine over.  Had strong spark in all four.  But still only running on
> two.
> Had a new spark plug wire which I tried and still the two would not fire
>
> when tractor was running.  Even switched the good wires to the bad plugs
> and
> vice-versa....same results.
>     My last test was I pulled the wire to the plugs which were not
> firing
> off the distributor cap while the tractor was runnining.  As I held it
> about
> 1/2 inch from the distibutor, it arced and fired.  Did the same with the
>
> other wire which wasn't firing.  Cleaned the contacts and reconnected
> the
> wires.  Same old thing.
>     Suggestions???  Is the distributor bad?  Tried to look close for
> cracks
> or wear.  Looking for the next step.
>
>     Thanks.  I don't contribute much anymore, but still lurk.
>
> Tim Nobles
> tnobles at netsync.net
>
> _______________________________________________
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> Remembering Our Friend Cecil Monson 11-4-2005
> http://www.antique-tractor.com/mailman/listinfo/at
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