[Healeys] Negative ground SU fuel pump question

richard mayor boyracer466 at gmail.com
Sun May 9 20:59:52 MDT 2021

Here's a photo of my pump with the cover removed.  The pump is an AUF305.
The yellow cylinder says 47n, + or minus 10%, 400V.   So, is this a
positive or negative ground pump?

On Sat, May 8, 2021 at 11:32 PM Kees Oudesluijs <coudesluijs at upcmail.nl>

> If you have the mostly used AUF301/AZX1308 with points you should not
> worry as these are dual polarity. However if you have an electronic version
> (EN or EP added to the model number, e.g. AZX1308EN = AZX 1308 Electronic
> Negative earth) you should not reverse polarity as this will damage the
> electronics.
> If you do not know what SU-pump you have remove the Bakelite pump cover.
> If there is a small metal or grey/yellow cylinder with 47uF printed on it
> (capacitor) it is dual polarity and you will be OK.
> If there is a green disk with electronic components and no points it is
> polarity sensitive
> If there is a small disk shape component between the feed screw and the
> small screw for the blades it is a diode and the pump will be polarity
> sensitive. Pos. earth pumps should have a red tape around the coil body.
> If it is a late pump there could be a very small more or less ball shaped
> item fitted to one of the pedestal screws to earth and the screw that holds
> the points blade which probably is a sort of bidirectional Zener diode or
> transil. Such a pump should be dual sensitive.
> When I rebuild my pumps I replace the original transil or diode with a 18V
> transil according to my own specs. The transil is fitted to one of the
> pedestal screws to earth and the screw that holds the points blade. If the
> pump has a capacitor fitted I fit an extra transil in parallel with the
> capacitor. So all my rebuild pumps are dual polarity.
> Kees Oudesluijs
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