[Healeys] S U fuel pump

Kees Oudesluijs coudesluijs at chello.nl
Tue Oct 20 10:16:47 MDT 2020


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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