For the purposes of freedom of information, here's an extract from my build thread. Motivated with info from Dickywhizz75 above :
With the Mini fuel level sender providing a resistance range of 30 Ohms (full) and 290 Ohms (empty) it was nowhere near the same as the Toyota instrument that used a range of 4-114 Ohms. I considered this idea of replacing the rheostat in the fuel level sender with a custom circuit board.
Making the custom fuel sender circuit board was a relatively easy process - pull apart the factory sender rheostat, make some measurements
Using a free PCB maker program called Circuitmaker, I copied the layout of the factory rheostat. The small custom board (37mm x 33mm) was designed to have twenty four 4.7 Ohm SMD resistors wired in series to get a ~5-113Ohm resistance range. It was a great way to solve the problem of mismatching ranges between the Mini and Toyota Starlet. I had a bare PCB milled and the board and realised that I'd screwed up the sweep angles so had to do it over again! Once the design was corrected and new boards milled, it was then screwed back onto the sender assembly
Soldering the tiny 0805 size SMD resistors (2.0mm x 1.3mm each) to the circuit board was fiddly but once done, the board was screwed onto the sender assembly.
Testing showed that the range was pretty dang close to the Toyota instrument. I actually made two sender PCBs so I've got a spare.
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-Alan
I blame my dad for my love of minis. I think I was conceived in the back seat of one
I also blame my Dad for me being 6' 1" - not really the optimum height for driving a Mini.