Talk Morgan Forums Morgan Sports Cars Morgan Three Wheeler & Super 3 Fuel gauge sender/rack

Does this mean the fuel gauge is calibrated to read 0% at 72 ohms then? Can it be recalibrated to read 0% at 75.5 ohms
My 280mm sender reads 0% after 160 miles though.

The specification sheet that comes with the sender says it should have 4mm clearance to the bottom of the tank and it is about that. I have not found any way to calibrate the gauge but I have not looked too hard as my contents indication isn't too far out.

The rev counter/fuel display is made by VDO, it seems to be based on their Ocean Link Range. Installation instructions are here:
http://www.mechanikadc.cz/wp-content/uploads/2014/05/MI-Dzm-CAN-Master-EasyLink-GB.pdf
and whilst you can select fuel level display and calibrate it from a button on the front of gauge it would unfortunately seem that the M3W version is probably preprogrammed and calibrated to suit the 240mm tube sender.

Seems NOT, because it reads more accurately.

On another note, anybody understand ( maybe OP Richard?) why the word "rack" is in the thread title?

I agree Ken. Have just measured my old original 250mm unit and it reads (as best as I can measure) 3 ohms with float at top of travel, and 70 ohms at bottom of travel. I see no reason why VDO would offer a different max resistance for longer sensors, and would guess the small differences noted by planenut were down to manufacturing tolerances.

The value of fitting the longer sender seems indisputable given the consensus of opinion that it gives the expected higher reading for any given registering fuel level below full.

First post explains thread title query BTW.

The small differences were not measured by me but come from the VDO data sheet. When I measured the resistance of both the 250 and 280mm units they were the same at full and empty (3 and 70 ohms). Maybe that is down to manufacturers tolerances as you say. Either way the 280mm unit gives a better indication of whats in the tank than the original, maybe not accurate but better.

And I've yet to see any fuel gauge on any car be accurate, in as much as they all read empty when in fact the tank is not... the "reserve" factor.

on my mazda the gauge never moves for the first 30 miles, then once it gets to 1/2 it falls like a stone, very quickly. SO basically i get 250 miles on the first "1/2" and 50 miles on the 2nd "1/2".
You just learn your vehicle.

Exactly like my 280mm sender in Mo until two days ago. Needed a cleaner ground it seems.

I took apart a failed float type water tank sensor on a previous boat. It just used a small magnet in the float to operate a range of reed switches along its travel length. These in turn switched a ladder of resistors to provide a crude potentiometer. If memory serves there were only four switches so large incremental jumps in the indicated level.

I suspect the VDO sensor to be of similar design.