[Healeys] Negative ground SU fuel pump question
coudesluijs at upcmail.nl
Mon May 10 09:48:27 MDT 2021
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.
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