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.
Simon
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.
Best
Achim
?
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