Did Your Citroen Traction Avant Fuel Gauge Stop Working?

Question

Please advise how to access the fuel tank sending unit on a 1956 Citroën Traction 11BL. Either I have lost the electrical connection or the ground, or maybe the float has sunk to the bottom of the tank. I have toyed with the assumption that since I have filled the tank with gasoline, the meter which is calibrated in liters of essence does not recognize the liquid which now fills the tank and therefore the gauge reads empty. Any and all advice sincerely appreciated.

Citroën Tech Tip

Thanks for your note. On a 6 volt system you always want to look for the ground to be the usual problem when something electrical does not work.

The sending unit operates by resistance in a coil of wire that the connection in the tank slides up and down on. When the tank is low with fuel, the connection is at the bottom of the coil with many windings. The higher the float goes in the tank, the fewer windings on the coil and thus the less resistance electrically. This makes your gauge on your dash head toward full. It starts off at about 1.5 volts and raises to the full 6 volts when the float is to the top and the tank is full.

If you have an electrical tester you want to gain access to the connections to the sending unit. This will be on the floor of your trunk under the floor mat. There should be a little trap door to gain access to the unit on the trunk floor.You will need a volt meter

of some kind, and a jumper wire preferably with an alligator clip on each end.

Disconnect the coil wire on the car, so that no damage happens to the ignition points, and then flip on the ignition key. Find the wire that is feeding power to your sender by touching the negative on the tester to a good grounding surface of bare metal in the trunk area. Then hook the positive end of the tester to one of the electrical wire ends leading to the sender. Once you find the positive connection you now know that you are at least getting current back to the sending unit.

Now make sure the connections are clean on the sender unit, and hook the jumper wire I mentioned that you needed to the other tab or screw connection on the sending unit. Clip the other end of the jumper wire to a good ground and then go see if your fuel gauge is working.

This is what I have found, over the years, to be the most common cause with Citroen Tractions and early Citroen D Series cars with 6 volt systems… A bad ground.

If that does not solve your problem, what I have found in rare cases is the cork fuel sender float in the tank has become water logged (or in this case fuel logged). Sometimes the new reformulated fuel can cause this to happen.

If that is the case you will need to remove the sending unit from the tank, and either replace it or find some type of coating to apply to the float that will stand up to fuel and seal the float.

Oh yes, and the next time you want to run your car, don’t forget to re-connect the coil wire.

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