[xk] SU fuel pumps

I’ve been away from the computer for a week, just now going through
about 15 digests, so once again I’m too late to pop into an interesting
discussion. How about a little history to round it out.

We have discussed fuel pumps several times on this list, and even going
back to the old original jag-lovers list, maybe even the british cars
list before that, so there is plenty of stuff in the archives.

There is a scheme posted somewhere on the website for putting a
transistor, a resistor and a diode in your old original pump to reduce
the current flowing through the points, which will make them last
longer. This mod was published by the Classic Jaguar Assn about 10 or 12
years ago, and they got it from some vintage MG folks. I believe the new
Burlens pumps are some slight variation on this basic theme. These new
transistorized pumps, and any old pump that has been modified, are
indeed setup only for positive or only for negative, and the transistor
used is different for each.

The SU pump as originally installed in our cars and on up through the
end of carburetted Jaguars in the 1970’s was not transistorized, and was
therefore not polarity sensitive. Beginning sometime in the 1950’s there
was a capacitor (aka condenser) inside which helped the points to last a
little longer. My 1950 Mark V pump didn’t even have this capacitor at
all, so the points arced something awful, and I have replaced the
points twice. The last time I rebuilt it I did the transistor and diode
modification, and now there is only the faintest discernible arc at the
points. I believe it ought to last the rest of my lifetime.

Rob Reilly - 679187

Rob:
Suggesting that an SU fuel pump will last your lifetime sounds like a
death wish.
Regards
BB----- Original Message -----
From: R,J,G,&KR xk120q@ix.netcom.com
To: Jaguar XK list xk@jag-lovers.org
Sent: Thursday, September 16, 1999 6:04 AM
Subject: [xk] SU fuel pumps

I’ve been away from the computer for a week, just now going through
about 15 digests, so once again I’m too late to pop into an interesting
discussion. How about a little history to round it out.

We have discussed fuel pumps several times on this list, and even going
back to the old original jag-lovers list, maybe even the british cars
list before that, so there is plenty of stuff in the archives.

There is a scheme posted somewhere on the website for putting a
transistor, a resistor and a diode in your old original pump to reduce
the current flowing through the points, which will make them last
longer. This mod was published by the Classic Jaguar Assn about 10 or 12
years ago, and they got it from some vintage MG folks. I believe the new
Burlens pumps are some slight variation on this basic theme. These new
transistorized pumps, and any old pump that has been modified, are
indeed setup only for positive or only for negative, and the transistor
used is different for each.

The SU pump as originally installed in our cars and on up through the
end of carburetted Jaguars in the 1970’s was not transistorized, and was
therefore not polarity sensitive. Beginning sometime in the 1950’s there
was a capacitor (aka condenser) inside which helped the points to last a
little longer. My 1950 Mark V pump didn’t even have this capacitor at
all, so the points arced something awful, and I have replaced the
points twice. The last time I rebuilt it I did the transistor and diode
modification, and now there is only the faintest discernible arc at the
points. I believe it ought to last the rest of my lifetime.

Rob Reilly - 679187