Fuel level sensor/gauge issues in the Mark IX

Hello, Saloons List. My petrol gauge in the Mk IX does not register tank levels (neither right nor left). How can I confirm correct operation of the tank sensors independently of the gauge? This is a restoration of a car that was dismantled by a PO so I am flying blind. the wire loom is new. Any help will be much appreciated.

Hi Iain, welcome back.

I’m not certain about the Mark IX, but generally you should get a full scale reading if you earth the wire at the sender.

I’ll give it a try and report back.
Thank you,

Make sure you have a good ground.

Yes, I will. Headed over to the shop in a few.

No ohms reading on left tank. Reading 17:5 ohms on right tank. Rocking car alters ohm reading in right. Gauge does not register at all even with grounding right hand sensor. Tentative diagnosis is bad sensor on left and possible bad gauge?

Someone correct me if I am wrong, but in testing the gauge, one should NOT apply a direct 12 volts as there is a reduction flux capacitor (!!!) that supplies about 10 volts to the gauges.


Yes, the IVR (Instrument Voltage Regulator) supplies the circuit with 10V.

@ILOBReno: Has the car sat for a long time? That neither work would suggest that either the tank switch isn’t changing the gauge over, or that the gauge, or IVR is duff.

If a Mark IX Jaguar has a flux capacitor, are we back to the future?

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I applied 12 v current to a spare Fuel gauge from a Mk II with no fault. It read full and held for several minutes without incident.


Thank you Andrew,
Are the two fuel tanks wired in series, or are they entirely independent? I want to sort out the problem at the sensors at first to be sure because getting back at the gauge is such a hassle!

The senders are separate. The tank switch changes the pumps and sender.

Right, that directs me to the gauge. I have received a new sensor for the left so tomorrow I’ll get on with that replacement and then address the gauge.
By the way, if anyone can weigh in on the best way to address putting the front and rear windscreens in it would be gratefully received. One method has the glass going in on the bench with a cord in the groove that then allows one to pull the lip of the seal over the body work. The alternate approach has the seal going in first followed by the glass.

As regards the windscreens.
The main problem often lies with the replacement rubber. For some reason the manufacturers don’t seem to be able to get this simple product right. Even if the seal is the correct shape the rubber is often the wrong hardness.
I had to reuse my old one which fortunately was in decent condition.

I have now replaced a faulty sender from the left tank and the gauge was indeed bad as bench test with new sensor (0-85 ohms) failed while a Mark II spare gauge checked out fine on that sand sender. West Valley in Reseda, CA refurbished the petrol gauge and we are good to go!

I really do like having dual pumps and tanks, much newer cars than ours will leave you stranded with a dead fuel pump.

Having all gauges and senders working perfectly is sweet…you are now approved for take-off :grinning:

Thanks for the encouragement. Last phase is reattachment of the dash wood, glove boxes etc. I have no idea what clips/hardware belong to this job, as I did not
do the dismantle. Any idea on this? I cannot find any help online.


you are asking in the right place…I pulled a lot of stuff from 2 x wreck MK7 some years ago, including most of the timber, but I cannot remember what was involved. I think bolts and screws are used rather than clips…look for “witness” holes

No doubt someone on here will know

I am still hoping someone with a MarkVIII or IX can help me figure out how the dash and glove boxes attach? The witness holes do not appear to match anything at hand.

I have a parts book. I’ll have a look in that to see if there are any pointers.