[xk] XK140 Fuel Sending Unit Problems

I recently replaced my XK140’s gas tank and at the same time
the leaking sending unit. My mechanic tells me that the first
replacement unit from XK’s Unlimited was bad. Their replacement
worked for a half-day and then went up to read ‘‘full’’ and
stayed there (until the ignition is switched off and then
reverts to zero. We then tried a universal Smith’s unit which
also malfunctioned. Resistance issues are now being checked and
further details will be furnished as available, but I’m
wondering what wisdom might be out there regarding similar
problems. Thanks.

Norm Weinfeld
San Francisco
1955 XK140 DHC 817243–
Norman S. Weinfeld
San Francisco, CA, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–

You probably have already thought of this but the sender unit body must be
correctly grounded for it work reliably. Don’t rely on the fixing screws to
the tank to achieve this. A separate grounding wire is needed.
BTW I put the expected resistance values in the archive some time ago.
Eric
Church Stretton, UK

http://www.aqua-mail.comSent with AquaMail for Android

On 14 January 2015 15:35:12 nweinfeld norman.weinfeld@gmail.com wrote:

I recently replaced my XK140’s gas tank and at the same time
the leaking sending unit. My mechanic tells me that the first
replacement unit from XK’s Unlimited was bad. Their replacement
worked for a half-day and then went up to read ‘‘full’’ and
stayed there (until the ignition is switched off and then
reverts to zero. We then tried a universal Smith’s unit which
also malfunctioned. Resistance issues are now being checked and
further details will be furnished as available, but I’m
wondering what wisdom might be out there regarding similar
problems. Thanks.

Norm Weinfeld
San Francisco
1955 XK140 DHC 817243

Norman S. Weinfeld
San Francisco, CA, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–

In reply to a message from Eric Capron sent Wed 14 Jan 2015:

Many thanks for getting back Eric, but yes, we’ve got the
grounding issue covered. The problem appears to be in locating
quality electricals. Everything so far appears to be erratic in
the extreme; in a word, junk…–
Norman S. Weinfeld
San Francisco, CA, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php

Hi Norm,
Purist heresy, an hard to believe, I know, but FWIW, “Smitty’s Hot Rod Supply”, or some close sounding name, was a source for a vintage gauge and “universal” sending unit that worked perfectly for my '27 RR Phantom One DHC whose sending unit had virtually dissolved. Took two tries R&R of tank to get excursion of arm to “match” tank volumes. IIRC ~$100 3 -4 years ago. Your mileage may vary. No affiliation, Yadda, yadda…

  Good luck,
      The Jag MavenOn Jan 14, 2015, at 1:13 PM, "nweinfeld" <norman.weinfeld@gmail.com> wrote:

In reply to a message from Eric Capron sent Wed 14 Jan 2015:

Many thanks for getting back Eric, but yes, we’ve got the
grounding issue covered. The problem appears to be in locating
quality electricals. Everything so far appears to be erratic in
the extreme; in a word, junk…

Norman S. Weinfeld
San Francisco, CA, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php

In reply to a message from Gary Singer sent Wed 14 Jan 2015:

Many thanks for the info Gary. I’m really not too worried about
‘‘heresy’’ of this stripe, More important to me is to get a gauge
that is reasonably accurate, so this suggestion could quite
conceivably be of practical use to my mechanic, if not to me
ultimately, as he does most of his work on vintage Rolls Royces.–
Norman S. Weinfeld
San Francisco, CA, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php

Norm,

I have a Smiths gauge testing box which was sold to Smiths agents and
workshops for checking the various types of gauges that they made and one of
the things it can do is to emulate a sender unit. From this I took the
standard resistance values for the E, 1/4, 1/2, 3/4 & F positions on the
gauge. When I bought my replacement sender for my 140 from Barratts (NA
etc), before fitting it I checked it over very carefully against these
values and I got sensible results from the sender. I also connected it to
the gauge and satisfied myself that by operating the float by hand I could
send the full range of values to the gauge from E to F. When I fitted it to
the tank I had to re-profile the float arm to stop it binding on the bottom
of the tank but as far as I can tell without actually filling the tank
(which I am not ready to do yet) it works.

I’m not suggesting that the Barratts unit is any better than anyone else’s
especially as I have a suspicion that they probably all come from the same
source but I feel that the prospects are good. Having said that I know that
Barratts do actually make quite a lot of electrical items themselves and
have a strong interest in getting them right.

On the unit that you had that worked then failed were you able to examine it
to establish why it had failed? The symptom that you describe suggests an
open circuit either on the resistance wire itself or that the wiper was no
longer touching the wire. Given the trouble you are having it might pay to
see if you can make that one work reliably by repairing/re-making it.

In general I agree with your comment about the quality of some repro
electrical parts and some of the items that I have bought have needed a bit
of tlc to get them right. (Bulb holders are a case in point).

Eric
Church Stretton, UK-----Original Message-----
From: owner-xk@jag-lovers.org [mailto:owner-xk@jag-lovers.org] On Behalf Of
nweinfeld
Sent: 14 January 2015 20:14
To: xk@jag-lovers.org
Subject: Re: [xk] XK140 Fuel Sending Unit Problems

In reply to a message from Eric Capron sent Wed 14 Jan 2015:

Many thanks for getting back Eric, but yes, we’ve got the grounding issue
covered. The problem appears to be in locating quality electricals.
Everything so far appears to be erratic in the extreme; in a word, junk…

Norman S. Weinfeld
San Francisco, CA, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]-- --Support
Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php

In reply to a message from Eric Capron sent Thu 15 Jan 2015:

Some time ago I needed a replacement sender unit and visited n
establishment that specialised in NOS Lucas old parts.

They had a number of Smiths sender units NOS and we tried some
with a multi meter. It was easy put the M/ meter across the
connections. If it’s working well th e needle should move
smoothly as the float is lifted

Many didn’t , I’d guess because of light corrosion on the
contact that slides on the windings .

Probably could be cleaned and fixed , but paying for a new one
, I took one that did work.

It’s probably worth checking with a multi meter before going
to the trouble of installing it.–
Ed Nantes SS
Melbourne, Australia
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php

In reply to a message from Eric Capron sent Thu 15 Jan 2015:

Eric,

A thousand thanks for your detailed reply to my post. I have
passed your observations on to my mechanic.

Best regards,

Norm Weinfeld–
Norman S. Weinfeld
San Francisco, CA, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php