Like many others, I have fitted the longer 28cm sender (VDO 2240-11000-280) in an attempt to get more meaningful fuel level readings. However I have found the % readings to be increasingly meaningless. Standing on the shoulders of giants, I decided to have a go at cleaning the sender unit resistance wires.

After disconnecting the battery and removing the sender from the tank, I unscrewed the base of the sender tube. On my unit the base was threaded but I understand that some are held in place by a separate nut. The outer tube can then be removed, exposing the rather delicate looking resistance wires.

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I then mounted the sender on a test rig and connected my meter on Ohms range between the sender output and the top mounting flange.

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This is a rather ‘busy’ picture (!) but hopefully you can see that before I cleaned the wires the resistance measured around 80Ω from the very bottom up to around 2/3 of travel where it jumped to around 20Ω for the remainder of the travel.

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I then carefully cleaned the fine resistance wires with some metal polish and repeated the measurements. This time, the resistance increased linearly between 77Ω at the bottom to 7Ω at the top. This results in a linear % readout on the fuel level display. Much better!

Planenut tells me that the wires may need cleaning every 12 to 24 months to maintain performance.

By the way, when the float starts to cause a change in resistance at the lower end of travel, the fluid level is around 37mm from the bottom of the tank. Therefore, if we assume a total tank volume of 40 litres, we still have a reserve of around 5.5 litres when the gauge reads zero%. Remember this is with the longer 280mm VDO sender and the reserve will be greater with the sender that Morgan fit at the factory.

I still intend to keep an eye on the trip mileage to determine when a fuel stop is needed, but at least the fuel gauge should be a help not a hinderance. Longer term, I plan to fit a tube type sender and seperate fuel gauge as pioneered by PaulR. Does anyone have examples of where to fit a 2 inch gauge in the M3W?

Andy