Talk Morgan Forums Morgan Sports Cars Classic Morgans (pre-CX) Problem med gauge.

I have a Roadster 3.0 2010. I have a problem with the fuel gas gauge. When the tank is full it shows "Full tank" then the gauge doesn't go down until almost half the tank is used up. After that the gauge stops at half the tank, then the gas is gone. Has anyone else had this problem?

You might do better to post the question in the Classic Morgan (pre-CX) or the Maintenance sections.
Welcome to TM

Welcome to TM KimLake, what you describe is fairly normal for a Morgan of that era

You could potentially have a sticking sensor in the tank, but that's fairly rare

there are electronic gizmos you can add into the circuit and re-calibrate, eg https://spiyda.com/gauge-electronics/the-gauge-wizard.html

However, most of us just brim the tank, reset the trip and refill at say 250 - 300 miles (Mog model and engine dependant)

Welcome to TM Kim. The fuel level sensor is suspect if the problem is as severe as you suggest. The sensor is integrated with the fuel pump so maybe replacing this assembly might be prudent. I guess you could remove it as an interim measure and reconnect wiring such that with ignition on the effect of moving the sensors float arm could be monitored on the gauge. To avoid fuel pump running whilst doing this test the nearby 6 pin pump driver module could be temporarily unplugged.

Greetings KimLake.

Yes, a common feature as Jon said. Whilst the cars do use well tried and tested Ford pump and sender units, from about 2005 it appears Morgan chose to stick a PIC microcontroller between the sender and gauge. My money is on the implementation of this ‘tech’ for the gauge feature.




The gauge on my old 2006 car wouldn’t come off of full until I had used about 3 gallons so decided to recalibrate the thing (a 2006 car is similar to a 2010 car in principle but has a different dash).

This is what I did. Filled the tank to the brim and then whipped the dash off. Connected a potentiometer in series with the gauge. Don’t think its too important which one of the two gauge wires you use, although somebody that knows about electrickery will probably correct me here... The POT value isn’t that important either although I think mine might have been a 5k that I had kicking around. Then with the ignition on, twiddled the POT around until the gauge needle just landed on the full point.




Whipped the POT off and measured its value then threw the POT back in the junk draw.




Replaced the POT with the nearest value resistor that I could find as a permanent fix. I used 15 Ohm here.




My gauge was quite normal after this little procedure.

Hi Kim. Same car - same issue! I'm so used to it now that I don't think about it: as already suggested by CooperMan, I just always zero the trip, brim the tank and then look to refill around 250 miles or so. Although the gauge is somewhat recalcitrant, I've never bothered trying any tech fixes (like Rog's), partly because I'm loathe to mess around behind the dash: the electronics back there are notoriously failure prone - and unobtainable as far as I know. One false move, and ... poof!

That’s an excellent point Nick