[Healeys] Negative ground SU fuel pump question

[John Spaur]

Which wire is connected to the pump body, the positive or negative wire?
 
From: Healeys [mailto:healeys-bounces at autox.team.net] On Behalf Of richard mayor
Sent: Sunday, May 9, 2021 8:00 PM
To: Kees Oudesluijs <coudesluijs at upcmail.nl>
Cc: healeys <healeys at autox.team.net>
Subject: Re: [Healeys] Negative ground SU fuel pump question
 
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 <mailto:coudesluijs at upcmail.nl> > wrote:
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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