Fuel gauge not registering properly

[Craig Balzer]

You said: "Expansion tank, didn't know about that, i'll investigate."

I extracted mine a while back and took a progression of photos. These many help.

It is located in very upper reaches of the left rear fender just forward of the filler tube. Captions may help.

It was wedged in place very tightly. The adhesive attaching the anti-rattle (?) padding also adhered mine to the inner fender

[cunpr]

Dear Craig,
Thank you, very helpful. that looks like you'd need to remove the main tank before getting to the expansion tank. Any idea where the charcoal filter is?

[Craig Balzer]

I can't see how you'd extract the expansion tank with the fuel tank in place.

Charcoal canister is on right side of engine compartment attached to the vertical panel of the US passenger footwell secured with a single through-bolt.
It is painted hammertone silver -- I ~think~ the same color as the air filter housings -- but I'm not sure

[Jeremy]

Paul, you gotta be the only forum member with a JCB in your car collection, with a sidehammer to boot (whatever that is, it sounds fearsome)

[cunpr]

Dear All,
Thanks for all the info and stuff on the other threads regarding the gauges.
Some feedback, I purchased a new fuel tank sender unit from SNG assuming my original would be the fault but no, both gave linear ohm readings when isolated from the car of approx 20 to 200, full to empty. I then connected them to the car's wiring whilst out of the tank and both resulted in an accurate empty reading on the gauge but with the float in the full position the gauge read no more than half full with either sender, new or old. I checked the instrument voltage regulator and I could see it was only giving 5 to 6 volts before breaking and then reconnecting. So I rigged up a temporary loom with battery voltage into the senders, then through the gauge, then to the cars earth, moving the float position had the gauge reading accurately from full to empty for both senders. However I noticed that the ohmage reading from the original sender seemed to vary despite the float being static. So conclusion is the voltage regulator is duff and the sender is probably on its way out.
So I've fitted the new sender unit and temporarily wired the feed to the gauge from the battery side of the voltage regulator and she seems to be working well. A new (semi conductor type) regulator is on the way.

One other point, I noticed something not noted previously, the gauge has quite a long delay after the float position is changed, presumably due to its being a bimetalic strip device, and this was most noticeable when it was descending, going from fuller to less full. The lag returning to completely empty was minutes or more. This obviously won't be a problem when driving but needs to be allowed for when testing. Presumably this is because the strip has to cool down for it to read lower, and in this heat the cooling down will take longer.
So if you are working with an original gauge allow enough time for the bimetallic strip to respond before deciding whether its working or not.

[cunpr]

Dear All,
Just seen this from 2010, "You can then use your meter to measure the output voltage and thus deduce the on:off ratio. To change that ratio (and thus the average output voltage), you'll need to adjust the adjustment screw in the base of the unit."
So the instrument voltage regulator can be adjusted? It looked like a sealed unit to me?

[cunpr]

Dear All,
Fitted the semiconductor voltage regulator and now all the gauges work correctly. Just got to fix the cooling fan switch now.

https://www.ebay.co.uk/itm/254355438991

[Paul Buckley]

Lovely colour!

Stateside car? I thought that no S3 cars came with wires.
Is it a conversion?
Or am I wrong?

[cunpr]

Lovely colour!

Stateside car? I thought that no S3 cars came with wires.
Is it a conversion?
Or am I wrong?

Thank you. Sable brown, cinnamon interior. on paper sounds awful but in the flesh strangely fitting to its lines. Thats the original paint, chrome (except for UK overiders), softtop, leather and carpets.
There seem to be quite a few with wire wheels.
Yes stateside car, according to original invoice wire wheels were a factory fit extra.

[jagwit]

Dear All,
Just seen this from 2010, "You can then use your meter to measure the output voltage and thus deduce the on:off ratio. To change that ratio (and thus the average output voltage), you'll need to adjust the adjustment screw in the base of the unit."
So the instrument voltage regulator can be adjusted? It looked like a sealed unit to me?

In that statement regarding "using your meter", it would be most important to specify WHAT meter, or otherwise HOW the meter is to be used. A typical digital Volt meter (set to DC) is likely to appear most confused, measuring "12V"and then nothing, "12V" and then nothing etc as if the probes are not making good contact.

Here is a higly relevant post: viewtopic.php?p=35094#p35094

[cunpr]

Lovely colour!

Stateside car? I thought that no S3 cars came with wires.
Is it a conversion?
Or am I wrong?

Thank you. Sable brown, cinnamon interior. on paper sounds awful but in the flesh strangely fitting to its lines. Thats the original paint, chrome (except for UK overiders), softtop, leather and carpets.
There seem to be quite a few with wire wheels.
Yes stateside car, according to original invoice wire wheels were a factory fit extra.

Just checked, the wire wheels were a $275 extra factory fit.

[cunpr]

Dear All,
A shout out for JDO instruments who repaired my broken Kienzle clock, excellent rapid service.
One thought, i understand the clocks go out of time because they are electrically driven, JDO calibrated mine for 13.2 volts but that voltage will vary as the cars sits and discharges and then re-charges as it runs. So what about supplying it from a voltage regulator, set at say 12 volts? Should be possible to do the calibration and then the constant voltage will avoid it loosing time? I doubt it can be calibrated down to run of the original 10v regulator but an aftermarket one set for 12V should fix the issue?

[MontanaDiver]

My sender failed this past Fall. I ordered a new one from SNG and it read over full, and at 60 miles it went to full. I ran out of gas with 3/8 indicating. I bent the arm for the float several times until I was able to get the indicator to read correctly. Okay, 5 damn times! I reset the trip odometer and start looking for fuel at 150 miles in town and 200 miles on highway.

[HarryFD]

I am working through a similar issue. In my new to me XKE, the fuel gauge never registered more than 3/4 full and the low level light would come on with 3-4 gallons left in the tank (as indicated that a fill would take16-17 gallons).

Yesterday, I filled the tank after the light came on and put in 16 gallons. The fuel gauge was showing 1/4 full. I removed the fuel sender. The tank was full (as expected).

When I looked at the plastic float it was 3/4 full of fuel. There appears to be a pinhole in the float that caused it to fill and give me bad readings.

Ordered a replacement from SNG Barratt that has a foam float. Will install upon arrival and hopefully I will be fixed.

[HarryFD]

I am working through a similar issue. In my new to me XKE, the fuel gauge never registered more than 3/4 full and the low level light would come on with 3-4 gallons left in the tank (as indicated that a fill would take16-17 gallons).

Yesterday, I filled the tank after the light came on and put in 16 gallons. The fuel gauge was showing 1/4 full. I removed the fuel sender. The tank was full (as expected).

When I looked at the plastic float it was 3/4 full of fuel. There appears to be a pinhole in the float that caused it to fill and give me bad readings.

Ordered a replacement from SNG Barratt that has a foam float. Will install upon arrival and hopefully I will be fixed.

Parts came in.

The float is of the same plastic cylinder design as what is in the car now. Oh well!

The new copper washers had an ID slightly smaller than the screw OD's. Drilled them out to fit.

Installed everything and everything seems to be working properly not.

[Ikebaddog]

Do not believe any gauge on a 50 year old Jaguar, just get to know the car by driving it