[Healeys] SU fuel pump polarity

simon.lachlan at alexarevel.plus.com simon.lachlan at alexarevel.plus.com
Sat Jun 23 01:23:09 MDT 2018

I think that’s a diode in there. These things only work one way.  See attached. (written for local club in UK).

I’d guess that you’ve got identical pumps but that, if you removed the diodes, you’d see that one was hooked up the other way round.



From: Healeys [mailto:healeys-bounces at autox.team.net] On Behalf Of hspethmann at t-online.de
Sent: 22 June 2018 23:18
To: healeys at autox.team.net
Subject: [Healeys] SU fuel pump polarity


My Healey:

BJ8 MKIII 1964

# L27347

pos. earth


Fuel pump for the last 20 years:

SU AZX1307

now with a slow, but steady clicking every 15 to 20 sec , when ignition is on.


I thought, the easiest solution is to change the pump with a spare pump I have in my trunk for about the same time as the first one. Both pumps look the same on the outside. Both pumps are wrapped in black tape.  But the label on the box of the spare pump says: AZX1307 neg. earth.  

In the archives I found a very instructive contribution by Steve Russel from Aug 2009. And it ended with the words: "A picture would be worth a lot of words right now."

So I removed the cap on both pumps to see if there is any difference in the wiring and took a picture, attached to this mail..  Both pumps look the same inside. You see the old pump on the left, the new one on the right.  Under the cap you see a piece that looks like a capacitor, labeled as BZX1013. But following the explanation with terminal 1, 2 and 3 clockwise beginning with the power input stud and ending with the internal ground terminal I suppose the "capacitor" is a diode. But when there is no difference in wiring between the old and the new pump, why could it be, that the old one looking like a neg. earth ran 20 years in a car with pos. earth?

I'm confused and hoping for your wisdom to shed some light on the problem.





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