[AT] Firing on two instead of four

[John Wilkens]

Well, let us kow when you solve the mystery!   John


At 04:44 PM 11/27/2006, you wrote:
>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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>>
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>
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                    In the wide-open spaces of NE Oregon