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+--- Thread: SU fuel pump (/showthread.php?tid=9287)
SU fuel pump - falcott - 05-04-2024
Greetings all. SU experts are requested to comment. I've just acquired a 6v SU fuel pump which does actually run. The incredible thing is that it is made from brass rather than the alloy or aluminium that I've always seen SU pumps made from previously. It's heavy!
Anyway, I'd love to find out what it might be from (Morris?), and whether it is positive or negative earth. From the cap it seems to be low pressure, I guess. I don't know whether that means it's mounted on the firewall or at the tank. Probably at the firewall. It doesn't matter to me anyway, since I have a gravity tank, but with the SU carb mounted rather high.
I've photographed the only markings on the pump that I can see (including some of the hammer marks when it obviously jammed!). Thanks.
RE: SU fuel pump - Peter Naulls - 05-04-2024
My old Morris 8 had a brass, bulkhead mounted pump. I'm not sure when they went over to alloy, post war perhaps?
RE: SU fuel pump - falcott - 05-04-2024
Yes, it does seem to be the correct vintage for my Special. I guess the Morris 8 was positive earth?
I wonder what it does to the electrics of the pump if it's positive or negative earth, and it's swapped around? Perhaps it doesn't make a difference...?
RE: SU fuel pump - Robert Leigh - 05-04-2024
There are very few things where polarity matters. If you change the polarity by putting the battery the other way round the dynamo is the thing to change because it relies on residual magnetism from its last operation. The residual magnetism can be restored to correct in relation to the battery by briefly closing and re-opening the contact breaker.
RE: SU fuel pump - Jeff Taylor - 05-04-2024
Hi Geoffrey,
Certainly here in the UK the Series I & II Morris 8's were negative earth, not sure about New Zealand though. I own a 1936 Series I Morris 8 Tourer. The brass bodies would have been fitted to early (from November 1934) M8's and to various other Morris vehicles probably those built prior to around 1935 after which they moved over to alloy bodies. As Peter has said the pumps are bulkhead (firewall) mounted on the M8. The M8 pumps were 6v LP (Low Pressure) AUA 26. The new pumps SU sell are mainly dual polarity but the originals were single polarity as far as I can recall.
Further information on the pumps and spare parts can be sourced from SU Burlen here in the UK:
https://sucarb.co.uk/?_gl=1*rct1hj*_ga*MTUwMTkyNTg2Ni4xNzEyMzE0NjQz*_ga_CJG69R6ZGH*MTcxMjMxNDY0Mi4xLjAuMTcxMjMxNDY0Mi4wLjAuMA..
https://sucarb.co.uk/su-fuel-pumps-spares/single-lp-pumps-kits.html
Jeff.
RE: SU fuel pump - John Cornforth - 05-04-2024
Hi
As far as I'm aware, SU fuel pumps with conventional coils and points are not polarity sensitive. Below is an extract from the SU repair manual of 1958 (AUC 9609A) which you can find here: https://www.pieterbolhuis.com/rileyclub/wp-content/uploads/2014/02/Book-No.137-SU-Carburreter-and-Fuel-Pump-Workshop-Manual-1958.pdf
RE: SU fuel pump - falcott - 05-04-2024
Thanks Jeff and John. Very good resources, and reassuring news about polarity.
RE: SU fuel pump - Chris KC - 05-04-2024
That's a thing of beauty. FWIW I overhauled a couple of SU pumps last year using the Burlen service kit - considerably cheaper than buying a new pump. It is not nearly as hard to do as I'd imagined it might be.
RE: SU fuel pump - falcott - 06-04-2024
Thanks Chris. I know of them, so I'll check them out. The pump runs, and I can suck the valve open and closed with my mouth, so I don't know how much I actually need to do to it. It's only to top up a slightly high SU carb anyway, so as long as it doesn't leak fuel it's probably all good.
RE: SU fuel pump - Chris KC - 06-04-2024
I agree, if it's running and pumping then it should be fine. Should it cease it's repairable.