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Fuel Gauge Reading

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#1 Sunbeam


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Posted 20 June 2020 - 12:51 PM

Hello all knowledgeable mini owners. I have just finished restoring a 1967 mk 1 and have a couple of problems. My fuel gauge is reading just over 1/2 full when filled . Could this be the sender unit, gauge or  voltage stabiliser ? Also when driving at 40 mph , ( according to my sat nav as a guide) the speedo is showing 60/65 mph , which it definately isn’t doing. Any ideas ? Appreciate any help. Stay safe all.




#2 Quinlan minor

Quinlan minor

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Posted 20 June 2020 - 02:03 PM

The gauge part: Disconnect the wires from the tank sender and connect the leads. The gauge should indicate 'Full'.

If not the gauge may be adjusted. Search for thread showing Moke Spider's 'How to' on that.

If it does, remove sender and check maximum and minimum resistance across the terminals and that the transition is smooth from one to another.

Look for witness marks on the float which would indicate it was catching on something inside the tank. 

#3 Sunbeam


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Posted 21 June 2020 - 08:38 AM

Thanks, I’ll give that a try today.

#4 Ethel


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Posted 21 June 2020 - 09:13 AM

I think the early sender units (and gauges) had different resistance. It could also be something mechanical with the float, there should be enough of a stub sticking out from the float arm to act as an indication or to get hold of with mole grips for some "manual stimulation".




Credit to DKLawson, who used to post on TMF:


“Minis before late 1964 had the 0-90 Ohm (empty to full) range that you mentioned.  That is comprable to some GM guage systems.

From 1965 on the classic Mini had a sending unit with a resistance range of about 270 Ohms = Empty to about 30 Ohms = full.  These are nominal values.  If you measure a Smiths sending unit it probably won’t match these values exactly.

To use an aftermarket gauge with the bayonet mount sending unit you will need a sender meeting the industry standard range of 240 Ohms = empty to 33 Ohms = full.  Your gauge will show empty a bit sooner than true empty but consider that a safety bonus to prevent you from running out of fuel.

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