Hello

Was wondering where to start to fix a fuel gauge that isn't working on my MK 1 Cooper S?

Check for sunken float on fuel sender in left hand tank. Make sure the fuel is low. Over to you, all you auto elec experts

Earth out the wire to the sender.

Take the wire off your fuel tank and hold it to a bare metal part (as GTO said above,nothing will short out, don't worry). if the gauge moves to full scale deflection then the sender in the tank is at fault (or the float has sunk, as stibbsy said).

If its not that, next test for 10 volts at the back of the gauge. One wire will come from a voltage regulator at the back of the gauge (light green when stock), this is where the 10 volts will be.

If there is not 10 volts here, then you need to check your 10 volt regulator attached to the back of your speedo for 12 volt supply, and correct wiring orientation. Or the regulator itself may be at fault.

If there is 10 volts at the back of the fuel gauge, then there may be a break in the wire to the fuel tank (check for continuity), or the fuel gauge itself may be at fault.

_________________
SooperDooperMiniCooperExpertEngineering

All garage work involves equal measures of enthusiasm, ingenuity and a fair degree of irresponsibility.

Thanks Mick. I had to take a call and cut my answer short.

Yes, that one is a great sanity check, and you only have to open the boot which is a bonus.

_________________
SooperDooperMiniCooperExpertEngineering

All garage work involves equal measures of enthusiasm, ingenuity and a fair degree of irresponsibility.

If all else fails, check there is resistance across the meter's terminals. I bought a brand new speedo once and the new fuel gauge was DOA. But dead fuel gauges are not common.

_________________
DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

I only have one wire connected to the sender unit in the boot. Not sure where the second one needs to connect too

Anyone have a wiring diagram?

Thanks all

Just been looking at diagrams on the net and I have found that one wire from the sender unit goes to the fuel gauge and the connection on the sender should go to earth.

If someone out there can post a photo of the fuel sender in the boot that would be great. At least it will show me which connection goes where

There's a small terminal attached to the sender where a second black earth wire connects onto the sender. You can see it on this image of the sender. The black wire runs back around the tank with the signal wire to the gauge, but earths to the body behind the tank beneath the passenger side indicator from memory.

_________________
SooperDooperMiniCooperExpertEngineering

All garage work involves equal measures of enthusiasm, ingenuity and a fair degree of irresponsibility.

Thanks mick I will give it a try over the weekend