[Healeys] S U fuel pump

Bob Spidell bspidell at comcast.net
Tue Oct 20 09:18:24 MDT 2020

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.


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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