[Healeys] Negative ground SU fuel pump question

Bob Spidell bspidell at comcast.net
Mon May 10 11:22:25 MDT 2021

The late Dave DuBois pursued the same retirement pastime on this side of 
The Pond. He designed a retrofit using the points to switch a power 
transistor, with the expectation that relieving the points of most of 
the current-passing duties would extend their life; he found that doing 
so caused the points to wear faster, as the current was insufficient to 
clean the points surfaces. He later designed a solid-state solution 
using an optical switch; I had him convert a couple pumps for me and 
although the conversion was very professional--and he bench tested them 
for 24hrs continuous--I had mixed success with them. My results with 
SU's SS pumps, either conversions or off-the-shelf has been inconsistent 
as well. I think Facet avoids this problem by having their pumps run 
more-or-less continuously. I tried transils and didn't get the expected 
result; I guess me and SU pumps just don't get along, but like some 
girlfriends I've had I stick with them anyway.

Dave also noted, as did I, that the points available at the time were 
pure crap. They came in unmarked white boxes and appeared to be made out 
of (shiny) silver--go figure--whereas tungsten is a dull metallic color. 
Maybe the situation has improved in the last few years, but I haven't 
bought any for a while.


ps. If the pump is fitted with a capacitor, and the capacitor has '+' 
and '-' marks it will be polarity-sensitive (hence the marks).

On 5/10/2021 8:48 AM, Kees Oudesluijs via Healeys wrote:
> Richard,
> Rebuilding SU-pumps is therapeutic and satisfying. I started years ago 
> after I retired. I still discover new things about them and keep 
> developing the technique and methods.
> I always prefer to keep the 3-layer diaphragm as it is far superior to 
> the later 2 or even single layer ones. As long as all three layers are 
> intact, reasonably supple, not cracked and can be (very carefully) 
> separated from each other without damage they are usually OK. When 
> cleaned (brake cleaner) and dried I dust them with a little talcum 
> powder to prevent them from sticking in the future and keep the rubber 
> in good condition. In the past I used some rubber grease. I still have 
> perfect original diaphragms from pumps that were fitted in the '50's. 
> One thing which is important is to take care with the Bakelite bridge. 
> Do not overtighten the fixing screws as the Bakelite is rather brittle 
> and cracks easily. However the plus side is that Bakelite can be 
> glued, and if bits are missing reconstructed, very well using araldite 
> or any other suitable epoxy glue. Same for the cap. It will leave a 
> very strong and lasting repair.
> Points are usually fit for sanding the worst pitting followed by 
> polishing them with flower paper. Old point may be preferable to new 
> points, the old ones are probably a better quality. They hardly wear.
> The main reason the SU-pumps are giving up is lack of use as electric 
> corrosion between the points will stop them working. I have done more 
> than 160.000miles in my first Jensen-Healey and never had one problem 
> with the fuel pump. Even after I laid up the car for about 10 years it 
> would still pump the fuel on my yearly start up of the engine. After 
> that it was left to its own devices and when I took it out in 2008 to 
> fit in my present J-H it failed! I took it apart, cleaned, inspected 
> it, polished the points and rebuild it with all its original 
> components bar the seals for fuel hose connectors. It has been working 
> flawlessly ever since and that was needed was a cleaning of the 
> points. Earlier I replaced the capacitor with a transil 
> (bi-directional Zener diode), 1.5 KE18CA. I now keep the capacitor and 
> fit the transil in parallel with it. It will decrease sparking 
> tremendously.
> In very old pumps single instead of double points are fitted and often 
> no capacitor is fitted at all from the factory. When rebuilding these 
> units I always fit a transil with or without a capacitor to protect 
> the points.
> If you want to carry a spare fuel pump, do not use an SU-pump. The 
> points will corrode in the boot after some time and it will fail you 
> when you need it. Better to get one of those $15 simple Facet fuel 
> pumps. They are crude, make a lot of noise but will get you home.
> Cheers,
> Kees

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