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Re: [Healeys] Austin Healey 100 Misfire Diagnosis.

To: healeys@autox.team.net
Subject: Re: [Healeys] Austin Healey 100 Misfire Diagnosis.
From: Bob Spidell <bspidell@comcast.net>
Date: Wed, 28 Sep 2022 16:45:30 -0700
Delivered-to: mharc@autox.team.net
Delivered-to: healeys@autox.team.net
References: <CAB3i7LJ7O3Z58YEjEbdVVdpz7Q_9ovaggKrJBXLiwLQ2ksnPrQ@mail.gmail.com>
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Distributor cap shorting out.


On 9/28/2022 3:24 PM, Michael Salter wrote:
>
> **
>
> This problem has plagued me for over 1000 miles.
>
> Today I had to drive some 200 miles and this is how it went:
>
> Starting from cold I experienced a persistent and irregular misfire.
>
> Pulling the choke out made no perceivable difference.
>
> Power was not much affected and the car cruised along well in top 
> overdrive with just regular periods of misfiring.
>
> Climbing slopes really made no difference, even when full throttle was 
> applied for 10 - 15 seconds.
>
> Misfire continued for some 90 miles with no change when the engine was 
> fully heated up.
>
> I could really do nothing to influence the rate of the misfire 
> although it did seem to be slightly less evident at low throttle settings.
>
> After 90 miles I stopped briefly to get fuel and upon starting off it 
> was quite evident that the misfire had disappeared almost completely 
> and remained that way for at least 80 miles after which it started to 
> misfire just a little as I came to the end of the trip.
>
> _POSSIBLE CAUSES_
>
> 1.Plugs â?¦ not like a bad plug. The misfire seems to be more than 1 
> cylinder and never came close to being the regular beat that 1 plug 
> misfiring produces. All the plugs have a healthy brown/ grey appearance.
>
> 2.Coil â?¦In my experience coils are very reliable but when they do fail 
> they tend to fail as they warm up and the problem gets worse as the 
> coil warms up
>
> 3.Points â?¦ a possibility but the dwell is set at exactly 60 degrees 
> and does not waver at all when the engine is running in the shop.
>
> 4.Fuel pump â?¦ if the engine was starving for fuel because of a fuel 
> supply issue caused by a blockage or failing pump the problem would 
> get worse when the demand for fuel increased, as in climbing a hill of 
> full throttle. This was absolutely not the case.
>
>
> Any ideas folks?
>
>
>

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    Distributor cap shorting out.<br>
    <br>
    <br>
    <div class="moz-cite-prefix">On 9/28/2022 3:24 PM, Michael Salter
      wrote:<br>
    </div>
    <blockquote type="cite"
cite="mid:CAB3i7LJ7O3Z58YEjEbdVVdpz7Q_9ovaggKrJBXLiwLQ2ksnPrQ@mail.gmail.com">
      <meta http-equiv="content-type" content="text/html; charset=UTF-8">
      <div dir="ltr">
        <div class="gmail_default"
          style="font-family:arial,sans-serif;font-size:small">
          <p class="MsoNormal" style="text-align:center;margin:0in 0in
8pt;line-height:107%;font-size:11pt;font-family:&quot;Calibri&quot;,sans-serif"
            align="center"><b><span
                
style="font-size:18pt;line-height:107%"><span></span></span></b></p>
          <p class="MsoNormal" style="margin:0in 0in
8pt;line-height:107%;font-size:11pt;font-family:&quot;Calibri&quot;,sans-serif">This
            problem has plagued me for over 1000 miles.<span></span></p>
          <p class="MsoNormal" style="margin:0in 0in
8pt;line-height:107%;font-size:11pt;font-family:&quot;Calibri&quot;,sans-serif">Today
            I had to drive some 200 miles and this is how it 
went:<span></span></p>
          <p class="MsoNormal" style="margin:0in 0in
8pt;line-height:107%;font-size:11pt;font-family:&quot;Calibri&quot;,sans-serif">Starting
            from cold I experienced a persistent and irregular misfire.
            <span></span></p>
          <p class="MsoNormal" style="margin:0in 0in
8pt;line-height:107%;font-size:11pt;font-family:&quot;Calibri&quot;,sans-serif">Pulling
            the choke out made no perceivable difference.<span></span></p>
          <p class="MsoNormal" style="margin:0in 0in
8pt;line-height:107%;font-size:11pt;font-family:&quot;Calibri&quot;,sans-serif">Power
            was not much affected and the car cruised along well
            in top overdrive with just regular periods of 
misfiring.<span></span></p>
          <p class="MsoNormal" style="margin:0in 0in
8pt;line-height:107%;font-size:11pt;font-family:&quot;Calibri&quot;,sans-serif">Climbing
            slopes really made no difference, even when full
            throttle was applied for 10 - 15 seconds.<span></span></p>
          <p class="MsoNormal" style="margin:0in 0in
8pt;line-height:107%;font-size:11pt;font-family:&quot;Calibri&quot;,sans-serif">Misfire
            continued for some 90 miles with no change when the
            engine was fully heated up.<span></span></p>
          <p class="MsoNormal" style="margin:0in 0in
8pt;line-height:107%;font-size:11pt;font-family:&quot;Calibri&quot;,sans-serif">I
            could really do nothing to influence the rate of the
            misfire although it did seem to be slightly less evident at
            low throttle
            settings.<span></span></p>
          <p class="MsoNormal" style="margin:0in 0in
8pt;line-height:107%;font-size:11pt;font-family:&quot;Calibri&quot;,sans-serif">After
            90 miles I stopped briefly to get fuel and upon
            starting off it was quite evident that the misfire had
            disappeared almost completely
            and remained that way for at least 80 miles after which it
            started to misfire
            just a little as I came to the end of the trip.<span></span></p>
          <p class="MsoNormal" style="margin:0in 0in
8pt;line-height:107%;font-size:11pt;font-family:&quot;Calibri&quot;,sans-serif"><u><span> </span>POSSIBLE
              CAUSES</u><span></span></p>
          <p class="gmail-MsoListParagraphCxSpFirst" style="margin:0in
            0in 0in
0.5in;line-height:107%;font-size:11pt;font-family:&quot;Calibri&quot;,sans-serif"><span><span>1.<span
                  style="font:7pt &quot;Times New Roman&quot;">     
                </span></span></span>Plugs â?¦ not like a bad plug. The
            misfire seems
            to be more than 1 cylinder and never came close to being the
            regular beat that 1
            plug misfiring produces. All the plugs have a healthy brown/
            grey appearance.<span></span></p>
          <p class="gmail-MsoListParagraphCxSpMiddle" style="margin:0in
            0in 0in
0.5in;line-height:107%;font-size:11pt;font-family:&quot;Calibri&quot;,sans-serif"><span><span>2.<span
                  style="font:7pt &quot;Times New Roman&quot;">     
                </span></span></span>Coil �<span>  </span>In
            my experience coils are very reliable but when they do fail
            they tend to fail
            as they warm up and the problem gets worse as the coil warms
            up<span></span></p>
          <p class="gmail-MsoListParagraphCxSpMiddle" style="margin:0in
            0in 0in
0.5in;line-height:107%;font-size:11pt;font-family:&quot;Calibri&quot;,sans-serif"><span><span>3.<span
                  style="font:7pt &quot;Times New Roman&quot;">     
                </span></span></span>Points â?¦ a possibility but the
            dwell is set at
            exactly 60 degrees and does not waver at all when the engine
            is running in the
            shop.<span></span></p>
          <p class="gmail-MsoListParagraphCxSpLast" style="margin:0in
            0in 8pt
0.5in;line-height:107%;font-size:11pt;font-family:&quot;Calibri&quot;,sans-serif"><span><span>4.<span
                  style="font:7pt &quot;Times New Roman&quot;">     
                </span></span></span>Fuel pump â?¦ if the engine was
            starving for fuel
            because of a fuel supply issue caused by a blockage or
            failing pump the problem
            would get worse when the demand for fuel increased, as in
            climbing a hill of
            full throttle. This was absolutely not the case.</p>
          <p class="gmail-MsoListParagraphCxSpLast" style="margin:0in
            0in 8pt
0.5in;line-height:107%;font-size:11pt;font-family:&quot;Calibri&quot;,sans-serif"><br>
          </p>
          <p class="gmail-MsoListParagraphCxSpLast" style="margin:0in
            0in 8pt
0.5in;line-height:107%;font-size:11pt;font-family:&quot;Calibri&quot;,sans-serif">Any
            ideas folks?<br>
          </p>
          <p class="gmail-MsoListParagraphCxSpLast" style="margin:0in
            0in 8pt
0.5in;line-height:107%;font-size:11pt;font-family:&quot;Calibri&quot;,sans-serif"><br>
          </p>
        </div>
      </div>
      <br>
    </blockquote>
    <br>
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