Faulty Petrol Level Sensor ?

[LaikaTheDog]

I have always suspected my petrol level sender unit is a bit dodgy, but now I get a fuel light on all the time,

all connections are good

when ignition is off the indicator drops to the left, with ignition on it moves to E, never higher
fuel warning lamp is lit.

how do i test the sender ?
how do i remove the sender ?
is there a way to emulate the sender to check the wiring and gauge/lamp without buying a new sender ?

solution so far- carry a jerry can !

[nebogipfel]

If my memory isn't failing me removing the wire from the sender (the one that goes to the gauge) and shorting it to a good earth should result in the gauge going across to a full reading thus proving that the gauge is OK and therefore the sender is almost certainly not

Hope this is correct

[1964 S1]

Keep the jerry can but you can also develop an ear for the amount of fuel left by opening the cap and bouncing the car enough by hand to hear the sloshing. Different depths, different sounds. Be careful, if it's nearly full it could come out the filler! MPG notes help. If you can't hear it, jerry time. On little elans it's easy to stick the filler with a long dowel to check tank fuel depth.

[LaikaTheDog]

nebogipfel, you were right, if you run the live feed to earth the gauge moves to full, so the gauge is working, the sensor was faulty

I removed the sensor and found that it was worn out.
the sensor works using a sandwich and two sprung rotating arms, the top of the sandwich is the wrapped wire that one of the rotating arms is pressed against, the lower part of the sandwich is a thin layer of copper over a fibre board, the lower rotating arm touches this. Both arms are attached together on a spindle that extends into the tank and has a float on the end, as the fuel rises the float rises turning the rotating arms in the sensor
The copper film in my case had worn all the way through were the arm was constantly moving back and forth as the fuel level went up and down. the lack of a copper surface meant that the sensor has no circuit to complete and so showed empty !

I simply put solder over the area worn out to recreate the surface, i then sanded it down level with the copper and now my sensor works better than ever !

[1964 S1]

Hello LTD, what did you use to reseal the sensor? Does your low fuel light work properly now? My gauge hasn't worked right since I purchased the car but the light works perfectly.

[LaikaTheDog]

it is not a sealed unit, it is just a pressed metal case with bent metal tabs holding the lid on....
i tested the gauge while it was off, it now works perfectly,
the really valuable bit that must remain intact is the coil of copper wire over the fibre board, without this the resistance does not work, suppose you could rewind it, but a new sensor is about ?50 exchange...is it worth the pain ?

[berni29]

I drove my previous (now deceased) +2 for about 5 years without a working fuel gauge and like the earlier post says you develop a sense for the amount of petrol in the car. Also the sloshing trick by putting your hip against the wing worked well for me. I never once ran out. Then I bought another +2 and swapped the sensor over. From then on I got a 3/8 reading when the car was full, and empty on empty. That was luxury I can tell you.

On the sticking a stick into the tank, you cannot do that with a plus 2, but I always did it when flying a little R22 helicopter. I think that many pilots do it to check the fuel before taking off.

Berni

[rgh0]

I had a similar problem in my S1 Esprit about 15 year ago. The coil in the level sensor broke. I removed it and adjusted the coil winding, joining the break on the opposite side from the moving contact. I ordered a new sensor which came about a month later. Since then I have never got around to changing it for the new sensor as the old one has worked perfectly for the 15 years since.

Rohan