[Healeys] SU fuel pump polarity

WILLIAM B LAWRENCE ynotink at msn.com
Sat Jun 23 09:27:39 MDT 2018

Better yet test with a multimeter set for continuity. You should have continuity in one direction across the diode and none in the other.

Hooking it up to a power source in the wrong direction will probably fry the diode. While that will be inconvenient you will at least know what the problem is...

Bill Lawrence

BN1 #554

From: Healeys <healeys-bounces at autox.team.net> on behalf of Bob Spidell <bspidell at comcast.net>
Sent: Saturday, June 23, 2018 2:39:43 AM
To: healeys at autox.team.net
Subject: Re: [Healeys] SU fuel pump polarity

Looks like they're both wired the same, and for neg. ground.  Try hooking them up to a 12V power source, and see which way makes them fire (pump).   If they don't run connected one way, try the other.  If it doesn't run right off the back disconnect lest you overheat the solenoid body.

Are both diodes labeled the same?


On 6/22/2018 3:18 PM, hspethmann at t-online.de<mailto:hspethmann at t-online.de> wrote:

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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