[Healeys] SU Fuel pump points

Mon May 25 14:22:49 MDT 2020

Points in an SU fuel pump should last a very long way. In my first car 
with the SU AUF301 (as in many A-H's 3000) it lasted at least 160.000mls 
or 8 years (1977-1985) in my daily driver Jensen-Healey. Never even 
touched the pump. After the car was laid up it was still started 
regularly every year without trouble until the intervals became larger 
and larger and about 5 years ago it failed. As my present Jensen-Healey 
did not have an original fuel pump, I took the one from my old car and 
rebuild it. The only thing wrong were the points. They had electrolytic 
corrosion big time. Cleaning and polishing the points (2000 grid) and a 
dusting of talcum powder between the three layers of the old fashioned 
diaphragm to make it supple again, had it up and running in my new J-H 
until this day, another 35.000mls. The trick is to set them up properly. 
All explained in the SU instructions. Very easy.  It is also imperative 
that the car is used on a regular basis.

These pumps are very easy to rebuild. It only takes less than an hour. 
Usually no new parts, apart from a gasket, are needed as long as you 
leave the valves and its seals plus air chambers alone. These usually do 
not need any attention. If it ain't broke, don't fix it. Check by 
blowing/sucking into the in/outlet if there is any leakage (make sure 
there is absolutely no fuel in the pump, inhaling fuel can be lethal). 
In some instances the points can be worn beyond repair and they have to 
be replaced, but even new points need to be cleaned, polished and set up 
properly (0,9mm top blade, 2,3mm lower bridge).

Fit the pomp body and the coil body together with the vent hole of the 
cap pointing upwards. Fit the pump in the proper orientation in the car 
(indicated on the body).

Failing points could cause the pump to run erratic leading to fuel 
starvation. Not a very common situation.

An SU pump incl. the points will nearly last you for ever, but it needs 
maintenance. Every year clean the points wit a bit of double folded 2000 
grid wet and dry and seal the cap with friction tape.

Main thing is these pumps need to be exercised regularly. Failing to do 
so will cause them to fail.

Most will be fitted with a capacitor, a cilindrical yellow/gray part 
fitted between earth and the spring blade with points. It works OK and 
it makes the pump dual polarity. Later pumps have a diode fitted between 
the power terminal and the points, this makes the pump polarity 
sensitive, turning around the diode will change the polarity. I always 
fit a transil, a sort of bidirectional zener diode, which make the pump 
dual polarity as well and limits the maximum voltage to prevent 
sparking. I often leave the capacitor in place as well.

Kees Oudesluijs

Op 25-5-2020 om 17:11 schreef simon.lachlan at alexarevel.plus.com:
>
> Basic question is: “How long, approx., should they last? (Yes, there 
> is a diode thing across them.)
>
> My car has been running OK. OKish…..I’d swapped back from Webers to 
> the three HD6s and had the car set up at the rolling road place. They 
> leaned the mixture settings somewhat, saying it would run better and 
> use less fuel. (A relative term). I noticed that it took much longer 
> to settle down after starting. Quite a lot of rude noises and much 
> play on the choke at intersections. And, when it was up to 
> temperature, I wondered whether it was quite right…was it a bit 
> sluggish or was I just used to the Webers?
>
> The other day, it hesitated and would have cut out. But, with one 
> bound I switched over pumps, and I was free! However, the pump – 
> double ended – had to come off for inspection. Both sets of points 
> were completely shot. I replaced them. Nasty, fiddly business. Now the 
> car starts much better and performs better all round. Surprisingly so….
>
> I installed that pump in 2012, +/-12,500 miles ago. So that’s +/- 
> 6,250 miles per set of points.
>
>  1. Would failing points give those symptoms? (I was/am surprised….I
>     though points either delivered 100% or failed 100%. I know that a
>     judicious thump on the bulkhead can work in the short term.)
>  2. How long would you expect SU points to last?
>
> Thanks,
>
> Simon
>
> Glorious weather here and forecast all week. Perfect Healey weather. 
> One is allowed out, but not really encouraged to go anywhere! 
> Maddening. Pubs are certainly shut. Anyhow, keep well.
>
>
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