[Healeys] S U fuel pump

[Kees Oudesluijs]

When properly fitted and adjusted the points in the SU pump do slide 
over each other.

Kees Oudesluijs



Op 20-10-2020 om 23:00 schreef jim via Healeys:
>
> Yep, the Bell System (think telephones)  ago found that "some" current 
> flow was necessary to break-down the oxidization
> unless the contacts were arranged to wipe or slide across each other 
> when operating..one solution was mercury wetted contacts
>
> Jim
>
>
>
> On Tuesday, October 20, 2020, 8:19:36 AM PDT, Bob Spidell 
> <bspidell at comcast.net> wrote:
>
>
> 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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