Talk Morgan Forums Morgan Sports Cars Maintenance & Servicing Fuel tank always full!

I now have unlimited mpg on the plus 8!
The fuel gauge reads full all the time and have now done the walk of shame twice. The gauge drops to empty with the power off. but reads full with the ignition on regardless of the amount of petrol in the tank. Have taken out the sender unit and tested it, the current varies with position of the float.
I can't understand the wiring- there are 2 wires going to the terminal on top of the 'stalk', one of which only runs to the mounting bolt for the fuel pump. A third wire connects to the 'body' of the sender presumably the earth this one disappears into the loom.
Any help out there?

Try the GoMog website

No help at all with fixing the gauge but my first Morgan, an 1981, had a fuel gauge that was almost as useless. If you zero the trip meter after filling up just keep an eye on the trip reading and fill up in good time. Mind you when my speedometer cable broke in France............

Have a look at this website it explains the wiring and covers an always full tank problem;

http://www.austin7.org/Technical%20Articles/Fuel%20Gauge%20Working/

"If the pointer is always at 'Full' - even when the tank is empty

Disconnect the wire to the 'T' terminal, if the gauge stays at ''Full'' then there is a fault in the gauge, if the pointer drops back to `Empty' then the gauge is OK and there is a fault between the gauge and the tank."

Sounds like you have a short either in wiring to regulator or in sender.

Low resistance when full and higher resistance as the tank empties.

When the gauge fails it'll normally show empty as would an open circuit like a cut or disconnected wire.

The gauges work on current flow rather than voltage iirc

Doesn't the voltage stabiliser sit within the fuel gauge circuit?

Does the temp gauge work OK (in Morgan terms that is)?

The first thing to check if you haven't done it already is the earth wire to the body of the sender unit. Run a temporary wire to a good earth and check it then.

My fuel gauge used to stick somehow...never bothered to do anything about it so I don't have any wisdom to impart i'm afraid.

I assumed it was linked in some way to the electrical side of things rather than the slender/float sticking in the fuel tank because it used to correct itself every time I stopped the engine and re started it. Never got caught out on a journey, but it could have easily done just that, however, if I hadn't discovered the problem through general observation early on in ownership.

Problem sorted! tested fuel sender unit (in the tank)-worked ok. replaced voltage stabiliser-still same problem. Used a multimeter to test wire integrity, no continuity from gauge to sender. The loom has a multi block connector under dash on offside. I split this, the rear part of the loom was ok, the wire from gauge to the connector was not continuous and was earthing out somehow, with ignition on and the multi block split gauge still read full. Ran a new wire from gauge to multi block problem sorted!
Now what was it shorting too? Will save up for a new loom it's 33 years old!