[AT] Firing on two instead of four

[Tim Nobles]

I haven't been back out to test any theories yet and may not make it back 
out until the weekend.  But I did "eye" the gap and thought it didn't look 
too close.  Will get the feeler guages out next time and report back. 
Thanks for the input.

Tim
----- Original Message ----- 
From: "Dudley Rupert" <drupert at premier1.net>
To: "Antique tractor email discussion group" <at at lists.antique-tractor.com>
Sent: Monday, November 27, 2006 1:36 AM
Subject: RE: [AT] Firing on two instead of four


> 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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