Petrol pumps

[les]

Some have twin points others have just one, anyone know why this is ? Maybe twin points last longer ? I ask because I’ve just replaced a pump that had twin points with a single.

[geoberni]

Well Double or Single Contact seems to be interchangeable without explanation.
Potentially, the double contact would (could) spread the current flow between 2 contact points, so halving the pitting that occurs at each point; but then there is the consideration that one side might always make or break before the partner, so that wouldn't happen.

See here: http://www.liblbc.info/images/SkinnerUn ... _4793a.pdf
On page 2 under 'The Contact Breaker Assembly' ... it just says fitted with 'one or two tungsten points'.
The same text appears in other model booklets too...e.g.
http://www.liblbc.info/images/SkinnerUnion/aua_222a.pdf

Certainly a bit odd to have an option like that without explanation.

[les]

Thanks for the reply and links. The original twin point pump I replaced wouldn’t stop ticking and delivered no fuel, a bit disappointing as I rebuilt it, maybe I should have fitted a new diaphragm, although it looked ok. However the single point replacement pump does deliver fuel.

[geoberni]

The main site of those links is something I only recently discovered and am still exploring.
It appears to be an American's personal project site from 2012 that has continued to be hosted but stalled in it's development.

Homepage: http://www.liblbc.info/

Some good stuff on vintage Lucas & SU manuals under the PUBLICATIONS menu, principally around Austin-Healey, Austin Mini Cooper and MGB , as that appears to be what the site owner has, but a good historical browse.

[Mark Wilson]

If you are rebuilding I recommend you do change the diaphragm. I rebuilt mine using the existing which looked OK and was pleased that it worked really well. Less pleased when I found petrol oozing from the diaphragm joint, took it apart, cleaned the faces and tightened the screws, still leaked. My unconfirmed diagnosis is that the diaphragm has become porous due to ethanol. Bought a new pump, will look at changing the diaphragm in the old one when I get time and keep it as a spare.

[les]

Yes I should have bought a new diaphragm, despite mine looking sound. There were no leaks just a continually ticking pump, which does seem to point to the diaphragm. Maybe I’ll strip it down later.

[Nickol]

Mine started leaking profusely earlier today. My neighbour had often said he could smell petrol when it was parked but I could never find any leak around the tank. Now I know. I have removed the pump and cleaned up the joint but not tested it yet. As above, if the leak persists - it was more a fountain than a leak, will order a new pump.