Fuel sender unit...Any ideas please..

[mrzigazaga]

Hi peeps..Ive been checking recent posts but only found min info... My fuel sender unit has completely stopped working..Does anyone know what was used in the 280i..was it ford?..cheers..Zig

[tempus]

Any power getting to it ?

[jeff m]

It sends a resitive ground to the battery backed guage.
Short the two wires, do you get FSD on the guage?

[mrzigazaga]

Hi chaps..sorry been out most of day..The fuel tank sender unit was rusted as well..where the coil paper bit was...(rusted off)..The gauge is stuck in the halfway position at mo and dont read any change..(I think the gauge is ok)..Many thanks..mark

Edited by mrzigazaga on Thursday 4th November 16:05

[jeff m]

I don't remember anyone coming up with "It's off a 1980........"
Maybe you could soak it in carb cleaner or brake cleaner and see if you can resurrect it.
Or possibly some clever bu66er can rewind it. Just need to know what max resistance the guage is expecting.

[mrzigazaga]

Hi chaps..This is from what the garage told me...Its not the fuel gauge on dash,its the sender on the tank..Apparently there is a coil of wire which has rusted beyond repair..Not quite sure what he means till i see it..thanks..zig

[adam quantrill]

Some people say.... you can get the same coil off an old mini. Trouble is even these are hard to come by now, I should think.

Just blank it off for now, do dead reckoning by miles and keep a spare gallon in the boot.

[Wedg1e]

mrzigazaga said:

Hi chaps..This is from what the garage told me...Its not the fuel gauge on dash,its the sender on the tank..Apparently there is a coil of wire which has rusted beyond repair..Not quite sure what he means till i see it..thanks..zig

The tank sender is basically a length of wire, that has a certain amount of resistance per foot (called, unsurprisingly, 'resistance wire').
Consider me FagCad sketch: if the gauge was wired directly across 12v the needle would bang straight across off the scale.
If you hang a length of resistance wire off the (-) side of the gauge, you can ‘slide’ the point at which it connects to ground (-), effectively adding resistance ‘in series’ with the gauge which makes it register lower. This ‘slider’ is connected to the tank float: as the float rises the slider gets closer to the gauge end, reducing the amount of resistance and making the gauge read higher.
In practice the resistance wire is wrapped around a flat ‘former’ to make it into a narrow coil, the slider then moves along one edge of the coil.
There are a couple of different ways of configuring the circuit but in essence this is the principle.

[mrzigazaga]

Cheers mate..so how do i fix it..bearing in mind im shyte at electrics..plus me eyes are frazzled..garage did say it was on like a piece of card?..can these be got from any where or is now a matter of making one out of silver foil and chewing gum..It did work before but was only working over half a tank..so i think its getting power..cheers..mark

Edited by mrzigazaga on Friday 5th November 14:27