Fuel Tank sender unit

[mach2andy]

I've just taken the above out of my tank to find that it looked pretty cruddy. The float arm was seized as well. I've taken the side cover off of the unit, and the inner workings appear in good order [I haven't actually checked the rheostat yet] and I've freed the arm up OK, but one thing I find odd is there does not appear to be any sealing medium between the side cover and the body of the unit?
Any thoughts??
ATB
Andy

[johnetype]

There is no sealing medium between the lid and the box.

From the photos, it all looks "normal" to me. You can check that the resistance changes in proportion to the position of the arm between 0 and 270 ohms (approximately iirc)

The low fuel light is illuminated by the arm bridging the contact on the Bakelite strip on the lid. If that isn't working when the arm is fully down you can try soldering the tag on the top plate (sender out of the tank!) as sometimes corrosion has created a lack of continuity here.

[cactusman]

Don't think there is any seal. Mine had none. The thing sits at the top so is rarely immersed unless you are rich . The fuel gauge resistance should not generate any spark as the wipers always in contact. There could be a small spark when the empty tank warning lamp finger makes contact but so long as the lid is on the sender the volume of vapour inside is minimal and probably has little oxygen there. I did add a 100 nanofarad ceramic capacitor between the lamp terminal and earth as a suppressor.

[JerryL770]

... the volume of vapour inside is minimal and probably has little oxygen there.

Actually the explosive range for gasoline vapour in air is quite limited and in general the vapour saturation level in a petrol tank will be well above the UEL (Upper Explosive Limit) which is only ~7.1% vapour by volume. The LEL is only ~1.2%