Talk Morgan Forums Morgan Sports Cars Maintenance & Servicing Faulty fuel guage

The fuel guage on my 2006 4/4 has started to go from zero to full as soon as the ignition is turned on and stays there irrespective of the amount of fuel in the tank. The tank is a Mulfab extended range tank fitted before l bought the vehicle and l assume is fitted with a more sophisticated system thsn the old fashion float which could get stuck (or am I wrong).

Before l start undoing bits on the tank what checks should l take?

Thanks
Chris

Check the electrical connections especially the earth.

And particularly the earth of the gauge. Normally all the dashboard instruments share a common earth, but I am not so familiar with the 4/4 of that era.

Usually the earth associated with the fuel gauge is at the tank end and connected to one leg of the sender, if not independently then via the sender mounting. In the latter case there will be an earth connection from tank to chassis to check.

If there was a earth problem wouldn't that result in no reading on the guage not the guage swinging to full?

It could even be an earth fault on the signalling wire between the gauge and sender. i.e. if the signal wire from the gauge to sender is connected direct to earth due to failed insulation along its length,, the gauge will read full. So try disconnecting at both ends and test the wire with a multimeter on ohms range to see if there is a spurious earth connection.

The fuel sender on a 2006 car is part of the in tank fuel pump assembly, and is an arm with a float

I might have a spare at the workshop

No not necessarily, a loose or poor connection i.e. dirty can cause the gauge to go to default which is full. It is the simplest place to start fault finding and eliminating factors before starting to dismantle the fuel system.

Did this start happening after you had filled the fuel tank? If it did had you filled the tank to first click of the pump or did you go beyond and kept filling through a number of clicks? If all this is the case then the float arm could be stuck in the up position, try giving the fuel tank a good shake when the fuel level is around half empty (as best you can estimate)

Managed to brim my tank full last weekend, gauge showed 3/4!

Think I may have a sender problem there