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

Earlier in this thread Richard Wood worked out the resistances of the 250mm and 280mm senders, and recommended a shunt resistor across the terminals of the 280mm sender.

See this post, and the comments that follow it.

Thanks John.

I have the 280mm sender unit, complete with Richard Woods shunt resistor fitted and to be honest it made little difference to the contents readings, they were still pretty random. The thing that did make a difference was to remove the sender unit, take off the metal cover tube and clean the two thin wires with some fine abrasive paper. After that the readings are fairly stable and the contents indicates a steady(ish) fall down to 0% over about 200 miles. I think that is about as good as it gets with this system. My recommendation is to clean the corrosion from the two fine wires inside the sender unit.

Planenut, here is what I am doing.

Changing to the longer sender just for a bit more accurate reading BUT adding an analog gauge calibrated for the sender at the same time. I like real gauges and dislike the vague displays of the MMC gauges.

I like real old school gauges but I do understand and appreciate the accuracy of digital. So in my M3W I have digital engine oil temp temp and differential temp but analog oil and fuel gauges.

While I was planning this I wanted the new sender to be able to be read by the ECU should I, or someone else, decide to use the oem setup.

I need to change the sender and the excuse why I have not, even though it is sitting on my desk is that I have been busy preparing for its installation. Also adding an oil pressure gauge as well., I just need to hook up the sender to the engine.




The M3W has not been started in two weeks.

While waiting for parts to show up I installed the 280mm Sending unit. Super easy to do and it worked with the OEM digital gauge AND when disconnected to worked with the new fuel gauge. I think the impedance might make it not work properly but having them both operational at the same time might be nice.

How did you connect up the gauge?

I ran a new cable above the frame tube from behind the seat back to the dash cowl. It was easy with the seatback removed.

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.



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.



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.



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?

Theres some work gone into that lot with a good outcome Bunny!

I used to have a couple of 2" gauges slung under the dashboard in a little mount but were hard to see so moved them here. I deliberately kept the holes in the leather part so that if I or the next owner wanted to get rid of the gauges a new piece of leather would be all that is needed to cover the holes.