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Re: [Healeys] S U fuel pump

To: healeys@autox.team.net
Subject: Re: [Healeys] S U fuel pump
From: Kees Oudesluijs via Healeys <healeys@autox.team.net>
Date: Tue, 20 Oct 2020 18:16:47 +0200
Delivered-to: mharc@autox.team.net
Delivered-to: healeys@autox.team.net
References: <1394757800.1379256.1603173043489.ref@mail.yahoo.com> <1394757800.1379256.1603173043489@mail.yahoo.com> <73d5d6ff-dfc0-b415-c04e-e18d66fab85d@chello.nl> <c8d0ee37-49cd-9bd5-a3c2-1ceb87ae51aa@comcast.net>
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Bob,

Did you fit the transil in the same way the diode was fitted? If so this 
is not correct. It should be fitted as the capacitor is fitted, between 
the small screw that holds the points blade and one of the bigger screws 
that fix the Bakelite bridge to the coil body. You can fit the transil 
instead of the capacitor or parallel to the capacitor. A diode is fitted 
in series with the points, a transil or capacitor is fitted over the points.

Kees Oudesluijs

Op 20-10-2020 om 17:18 schreef Bob Spidell:
> The late Dave DuBois, who designed the transistor-switch fix, quit 
> doing the conversions when he found the reduced voltage cross the 
> points allowed them to oxidize. I tried the transil fix, but didn't 
> get much more longevity than a stock points setup with a diode; I do 
> know some have had better luck with them.
>
> I have a points/diode pump in my BN2 that works well, but I only have 
> a few hundred miles in the car. I've lost track of what I've got in my 
> BJ8.
>
> Bob
>
> On 10/19/2020 11:31 PM, Kees Oudesluijs via Healeys wrote:
>>
>> When rebuilding SU electrical fuel pumps I ad a transil (e.g.. 1.5 
>> KE18CA) over the points, parallel or in stead of the capacitor if 
>> fitted. This reduces the max voltage across the points to 18V instead 
>> of several hundreds when the contact is broken and the points spark.
>>
>> It is also important to clean and polish the points using flower 
>> paper (2-3000 grid), also when new!!
>>
>> A transil is more or less a bi-directional Zener diode. They cost 
>> next to nothing. I buy them in bulk and pay about $0,15 but when 
>> buying only one expect  to pay between $1 and $5. Ebay is an 
>> excellent way to source transils (mainly from China).
>>
>> A transistor circuit similar to those used in early transistorised 
>> ignition systems does a similar job by limiting the current through 
>> the points
>>
>> Kees Oudesluijs
>>
>>
>>
>> Op 20-10-2020 om 07:50 schreef Ray Juncal via Healeys:
>>> I'm rebuilding a couple of early S. U. fuel pumps for my 100. In 
>>> checking my reference files I came across an article from the MG 
>>> club about adding a transistor circuit to reduce the amps across the 
>>> points. That would keep the points from burning and extend the life 
>>> of the points. Has anyone on the list tried this? The author of the 
>>> article claims he has 20,000 miles on the conversion and new looking 
>>> contact points. Thoughts, comments, suggestions.....
>>> Regards
>>> Ray
>>>
>>>
>>
>
>
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    <p>Bob, <br>
    </p>
    <p>Did you fit the transil in the same way the diode was fitted? If
      so this is not correct. It should be fitted as the capacitor is
      fitted, between the small screw that holds the points blade and
      one of the bigger screws that fix the Bakelite bridge to the coil
      body. You can fit the transil instead of the capacitor or parallel
      to the capacitor. A diode is fitted in series with the points, a
      transil or capacitor is fitted over the points.<br>
    </p>
    <p>Kees Oudesluijs<br>
    </p>
    <div class="moz-cite-prefix">Op 20-10-2020 om 17:18 schreef Bob
      Spidell:<br>
    </div>
    <blockquote type="cite"
      cite="mid:c8d0ee37-49cd-9bd5-a3c2-1ceb87ae51aa@comcast.net">
      <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
      The late Dave DuBois, who designed the transistor-switch fix, quit
      doing the conversions when he found the reduced voltage cross the
      points allowed them to oxidize. I tried the transil fix, but
      didn't get much more longevity than a stock points setup with a
      diode; I do know some have had better luck with them.<br>
      <br>
      I have a points/diode pump in my BN2 that works well, but I only
      have a few hundred miles in the car. I've lost track of what I've
      got in my BJ8.<br>
      <br>
      Bob<br>
      <br>
      <div class="moz-cite-prefix">On 10/19/2020 11:31 PM, Kees
        Oudesluijs via Healeys wrote:<br>
      </div>
      <blockquote type="cite"
        cite="mid:73d5d6ff-dfc0-b415-c04e-e18d66fab85d@chello.nl">
        <meta http-equiv="Content-Type" content="text/html;
          charset=UTF-8">
        <p>When rebuilding SU electrical fuel pumps I ad a transil
          (e.g.. 1.5 KE18CA) over the points, parallel or in stead of
          the capacitor if fitted. This reduces the max voltage across
          the points to 18V instead of several hundreds when the contact
          is broken and the points spark. <br>
        </p>
        <p>It is also important to clean and polish the points using
          flower paper (2-3000 grid), also when new!!</p>
        <p>A transil is more or less a bi-directional Zener diode. They
          cost next to nothing. I buy them in bulk and pay about $0,15
          but when buying only one expect  to pay between $1 and $5.
          Ebay is an excellent way to source transils (mainly from
          China).</p>
        <p>A transistor circuit similar to those used in early
          transistorised ignition systems does a similar job by limiting
          the current through the points<br>
        </p>
        <p>Kees Oudesluijs</p>
        <p><br>
        </p>
        <p><br>
        </p>
        <div class="moz-cite-prefix">Op 20-10-2020 om 07:50 schreef Ray
          Juncal via Healeys:<br>
        </div>
        <blockquote type="cite"
          cite="mid:1394757800.1379256.1603173043489@mail.yahoo.com">
          <meta http-equiv="content-type" content="text/html;
            charset=UTF-8">
          <div class="yahoo-style-wrap" style="font-family:Helvetica
            Neue, Helvetica, Arial, sans-serif;font-size:16px;">
            <div dir="ltr" data-setdir="false">I'm rebuilding a couple
              of early S. U. fuel pumps for my 100. In checking my
              reference files I came across an article from the MG club
              about adding a transistor circuit to reduce the amps
              across the points. That would keep the points from burning
              and extend the life of the points. Has anyone on the list
              tried this? The author of the article claims he has 20,000
              miles on the conversion and new looking contact points.
              Thoughts, comments, suggestions.....<br>
            </div>
            <div dir="ltr" data-setdir="false">Regards</div>
            <div dir="ltr" data-setdir="false">Ray<br>
            </div>
          </div>
          <br>
          <br>
        </blockquote>
        <br>
      </blockquote>
      <br>
      <br>
      <fieldset class="mimeAttachmentHeader"></fieldset>
      <pre class="moz-quote-pre" 
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