[Healeys] Fuel pumps (AGAIN!)

Kees Oudesluijs coudesluijs at chello.nl
Thu Nov 29 03:14:42 MST 2018

It is not uncommon that a car´s service sheet also included the SU-pump 
(clean the points every service), e.g. Lotus Eclat/Elite. However I 
never did and I have had no problems. I used my car as a daily driver 
but it had to live outside all year. Nowadays the car is pampered in a 
heated garage and is mainly driven when the weather is suitable for open 
top driving except for long trips abroad.

The pressure delivered by an SU-pump depends on where the pump is 
situated. If it is fitted under the bonnet it should be a so called 
low-pressure or suction pump delivering 1,8psi (e.g. some Austin-Healey 
Sprite/Mg Midget). You can often recognise this pump by the 2BA screw 
(same size as the screws that hold the coil housing to the pump body) on 
the coil housing for the earth spade. If the pump is fitted near the 
petrol tank it should be a so-called pressure pump delivering 2,7psi 
(e.g. MGB) or 3,8psi (Austin-Healey 3000, Jaguar 6-cyl. cars MkII, 
E-type etc., Triumph Stag, Jensen-Healey a.o.). The high pressure pumps 
can be recognised by a smaller 4BA screw for the earth spade. The 
pressure is fixed and is controlled by the spring fitted under the 
diaphragm.  All pumps are identical as far as the coil housing, points 
system, diaphragm are concerned. The differences are in the pump body 
but this has no effect on the pressure, mainly on the variation of 
delivery pressure and flow rate. Some cars have the h.p. pump fitted on 
the chassis open to the elements (e.g. MGB, A-H), others have it 
protected in the boot (e.g. J-H).

There are three types of spring, the low pressure 1,8psi spring can be 
easily recognised as the wire is rather thin and it has more coils, the 
2,7 an3,8psi springs have less coils and look identical to each other 
but the 3,8psi spring is slightly thicker and should have a (faint) dab 
of red paint.

If the SU-pumps would have been so unreliable as some of you claim, they 
would not have been used on such a large scale. Many millions of cars 
have had them in the 1930´s through to the 1990´s, from the humble 
Morris Minor to Rolls Royce.

Sure, the early ones did wear the points rather quickly because of 
arcing/spark erosion, but this was counteracted by proper maintenance 
which was usually every 1000 to 3000miles in the 30´s up to the 50´s. 
The wear was significantly reduced by using a simple capacitor (very 
like the capacitor in the points distributor), then a diode and lately 
Burlen fitting a transil. The pumps are dual polarity except when a 
diode is fitted.

However spark erosion is not the main problem, that is electrolytic 
corrosion due to lack of use and dampish conditions under the cover 
because of improper ventilation like no tubes connected from the pump to 
a dry area of the car (boot) or no rubber band or friction tape on the 
joint of the cover and coil housing or damp storage.

I am not sure if the quality of the points you buy today is less than 
the old ones. I have never used them. I still have NOS points to replace 
worn points, but more often than once cleaning and repolishing the old 
points will do.

Kees Oudesluijs

> Not trying to reinvent the wheel, David, just get a fuel pump that 
> lasts.  Others have had good service from points pumps like you, but I 
> haven't.  I'm not doing anything unusual; if you get them installed 
> and they don't leak and they run that's about all you can do--there's 
> no trick or secret to installing them that I know of.  Mine just keep 
> failing, with between a few hundred and up to 15K miles of service 
> (this over about 140,000 miles I've put on my BJ8).   I will say I 
> have driven through some serious downpours, so water entry into the 
> switching compartment could be a problem, but some of the failures 
> didn't get drowned.
> The points can be problematic, else SU wouldn't have gone from:
> 1) no arc suppression
> 2) capacitor arc suppression
> 3) diode arc suppression
> That is to say, SU wouldn't have gone to the expense and labor of 
> installing capacitors and diodes if there wasn't some issue with 
> reliability or longevity.  I tried all three, with results as noted.  
> I've installed the out-of-the-box, rebuilt and adjusted them myself, 
> installed SS switching mechanism, used capacitors, diodes, TVSes, 
> transistors and installed SU electronic out-of-the box with 
> predictable results.  I do recall your dad either writing or saying 
> that they used to take the pumps out and service them--cleaning the 
> points and adjusting the mechanism I presume--at 15K mile service when 
> he worked at BMC (or was it BL, don't recall), so they aren't 
> typically bulletproof forever.
> Maybe I pissed the SU gods off somehow; though both my sets of SU 
> carbs have been all but bulletproof, and the basic points-type in my 
> BN2 has worked for a few hundred miles.
> Bob
> On 11/28/2018 9:50 AM, healeydoc at gmail.com wrote:
>> I do not understand the problem with the SU pump that everyone feels 
>> that they have to re invent the wheel. I have using the standard SU 
>> pump with points in my Healey for almost 75000 miles and never had a 
>> failure.
>> We also have been installing the standard SU points pump here at the 
>> shop on every car we do for over 40 years
>> Everything from Healey’s, MG’s and Jaguar’s and had very few failures.
>> David Nock
>> healeydoc at sbcglobal.net
>> 209 948 8767
>> www.britishcarspecialists.com
>> Help us have our Founder Norman Nock inducteed into the
>> British Sportscar Hall of Fame, You can vote for your favorites
>> by visiting the site at.
>> www.britishsportscarhall.org
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