Fuel sender needed

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sleepy0905
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Fuel sender needed

Post by sleepy0905 »

Hi does anyone have a fuel sender spare they want to sell as mine is hadit it is not reading correctly and reads all over the place during accelleration and under braking and round corners.
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jeremy
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Post by jeremy »

I'm not sure how these work but it sounds as though its simply recording the fuel as it sloshes around in the tank. My TD one (TD's have the extra tank) reads full for anything up to 175 miles but is fairly accurate after that but I generally fill the thing full and run for 400 miles or more before filling up. It does not swing around which suggests that there must be some form of damping somewhere.

When Smiths introduced the thermal gauges in the 1960's they said the reason was that as they were slower to react they were more accurate - which might have been true - they certainly looked it!

The reason I'm saying all this is that both thermal and the earlier moving iron gauges used the same tank unit, and if your problem is a lack of damping I doubt if the tank unit is at fault.

When I got my TD the gauge was not working well and this turned out to simply be that the connector had pulled off the tank unit - cleaning and refitting cured that problem - but I think its quite common. from what I remember the flat wire runs under the back seat and through the hole in the floor to the tank. What was surprising was that it was sandwiched by the black plastic bung in the floor covering the sender unit - and I suppose had moved or the insulation had shrunk over the years.

The only fault I can think of with your sender unit could be failure of the resistor element (carbon track?) which has for example worn through and is providing an intermittent connection. This could be tested by removing the unit, and connecting it to a resistance meter and slowly moving the float and looking for rapid and significant changes in resistance. This is one of those circumstances where an analogue meter would be an advantage!

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sleepy0905
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Post by sleepy0905 »

Thanks it is the sender at fault i do have a spare but it doesnt record full tank but that one is stable the sender that is in has worn brass contacts on the float which means it moves up and down to freely i have even tried bending the spring contacts to make it grip a bit more but with no luck so it is a replacement job.
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Way2go
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Post by Way2go »

sleepy0905 wrote:the sender that is in has worn brass contacts on the float which means it moves up and down to freely
I dont know this device but know electronics and this does not sound like the fault. Damping is not usually mechanical but electrical or electronic. Free movement of the float is surely necessary so that it doesn't stick and read wrongly.
I would check if you have a capacitor and resistor somewhere across the meter for damping the reading. Failure of either R or C would give the fault you describe.
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sleepy0905
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Post by sleepy0905 »

On removal of mine the bottom has fell out of the sender so the slightest movement of the fuel moves the float oll over the place So i so desperately need a new sender the alloy can has corroded and the bottom had fell of as a disk which has been recovered out of the tank.
PLEASE PLEASE does anyone have a spare one lying around.
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DavidRutherford
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Post by DavidRutherford »

Yes.

But can you send me your old one to plug up the hole in the top of the tank I remove it from?
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sleepy0905
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Post by sleepy0905 »

David i have sent a PM
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sleepy0905
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Post by sleepy0905 »

I now have one i got it from a scrappers for £3 and its cured all the problems .
Thanks to everyone who offered parts or support.
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Post by Vanny »

just to clarify, this isnt the sort of fuel sender with an arm at one end and a float on it, the sender on the BX is a totally sealed unit which comprises and outer cylinder with a diaphragm inside and works something akin to a normal car damper to stop it sloshing about. From what i can tell its a glorified rheostat and the resistance based on the position of the diaphragm within the tube. The resistance is so small that once they start to wear they decent into mass broken ness very quickly. There not really repairable as you'll never be able to ge tthe resistances just right!


Strangely though there exactly the same for diesel and petrol (i have a 16v sender unit in mine, MattW has a 1.4 petrol one in his diesel BX), so theres at least a healthy source of them!


Anybody have any suggestions on how to store them?
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