Replacing fuel sender

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woody rocks

woody rocks

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Sussex
Had to replace leaking fuel tank so decided to replace fuel sender unit at same time as it was giving inaccurate readings. (ie, thought tank was almost empty, put in 25ltr and fuel gauge showed full). Previous owner says he replaced sender recently. The vehicle is negative earthed and the old sender only has one terminal. The new unit has three, two vertical and one flattened down. Britpart – Oh dear I've read about their reputation. If I connect to flattened terminal on the new sender the fuel gauge shows full. (measured 22 litres of fuel in new tank) If I connect to the positive vertical terminal no reading on fuel gauge. What is going on? Do I need to earth the new unit as well? I do not want to short something.
 
The S3 book only describes a single or twin terminal sender. The twin terminal is for the diesel with a low fuel warning light, terminal T from the gauge, terminal W from the low fuel bulb and the earth via the body. Mine's a single terminal one, dunno about a three terminal. Could one be an earth? Is it welded directly to the metal of the body? Can't see why you want a fused +ve on the fuel sender.
 
Last edited:
The response from the dealer who sold me the part – online – is as follow:

The flattened down tab on the new unit is an earth, so you will need to
make up an earth lead to connect to this.

Try connecting the lead from the gauge to one of the upright terminals
to see if the gauge works. You may need to try each terminal as it may
affect which way around the gauge works.

Will have another go when return from holiday, thanks for the advice
 
That sounds about right, later ones had a remote earth so that if theres a fault you dont run the risk of a spark near the tank, not good.
Run the earth wire well away from the tank before you ground it, dont use one of the tank mounts as a ground.
The correct terminal will work as it should, if you connect the wrong terminal to the guage, the guage will only show full when the tank is empty.
 
Are these senders wired up with a terminal at each end of the pot and the wiper to earth?
 
I was going to have a look at the sender unit this weekend after holiday but other issues have come up with MOT fast approaching. One is a number of oil splashes appearing on wheel rim, I have had wheel off, no sign of brake cylinder leaking and brakes dry, no sign of anything leaking behind wheel. Tried to attach pic of wheel rim but not sure how. Plus took landy for a couple of spins and the first few times you brake it was lurching alarmingly towards the kerb –*quite unnerving. Appreciate your thoughts
 

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Finally got round to installing the sender unit after holidays etc, earthed to chassis from flattened terminal and gauge lead to the appropriate terminal. Tank had about 1 inch of fuel in it registering halfway between empty and quarter full, the same as the sender unit being replaced. Put in 25 litres and now gauge goes off the scale, I would expect it to be showing about nearly 2/3rds full. Same problem as old gauge showing more fuel in tank than there actually is.
Any idea as to what might be going on?
 
Voltage regulator attached to the clock behind the dash. Try cleaning the contacts first but they are mechanical and prone to wearing out.
 
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