Before you go through the trouble of pulling out the sending units, get an VOM and see of you can get a reading at the plug. You should get about 10 volts to the unit. Check the value between the terminals and see if you get any value other than 0. If you get nothing, most likely the sender o bad.
I’ve had problems with earlier senders where the terminals oxidize of corrode and loose conductivity. A little bit of cleaning and they were fine.
Hi Mark, I’m in the process of getting my fuel gauges to work. The fuel tank sending units are very easy to access behind the tail lights. I removed mine without a hitch, very easy job. I’m going to replace the one on the right side, it was a bit crusty and the arm with the float attached wasn’t moving very well even after using WD-40 on it. The green internal wire broke loose from it’s terminal also but the float was still good. The one on the left side was still pretty decent looking and the float arm moved freely. The float did have some fuel in it so I was able to use the float from the right side. Anyway I ordered a new right side sending unit on ebay today so hopefully that will fix it. I noticed the left side(drivers side in the US) has a red round plastic piece around the wire terminal and the right side has a white plastic piece. The senders are specific for each side as you probably know.
1 Like
Or the windings that are the rheostat are worn away…
Jeep suffered that malady… New module, all well…
Carl
1 Like
It’s possible, but chances are it will fill up again because it is actually leaky. I tried it on both sides and both filled up a bit within two years. It works, though!
Yes, senders are side specific.
Problems with my '85 s3:
With my old sender still in place, I found another ground for the sender lead - same reading, about 1/2 on the dash gauge.
I shorted sender lead to ground, gauge goes to full.
I hooked up a new sender while it was sitting on the rear bumper, it reads about 60 ohms between the terminals, but the upper limit of the arm does not hit the limiting tab, and the gauge on the dash only goes to about 5/8 full.
Do you usually see the arm hit the limiting tab ?
I don’t understand…
Are you bench testing it or you’ve put the sender in the tank , filled up and it still shows 5/8 full?
**
I seem to recall someone even bending the limiting tab to get a ‘full’ reading, Louie…?
The tab is likely there for a reson - but what actually preventing the arm from reaching the tab?
frank
xj6 85 Sov Europe (UK/NZ)
**
Hanging up on the unwound part of the rheostat.
The wiper arm,that is…
Carl
ok, I pulled the new unit out of the bag; reattached digital ohm meter. Reading got to about 29 ohms at upper limit, arm touching the limiting tab. The float is just hard foam, fyi.
All of this is being done while new unit is sitting in the boot — Reattached to leads to dash gauge – I got about 15/16ths to FULL on gauge – at the low end of arm travel, dash gauge reads empty/zero, — all good . I’ve had British cars 50 yrs; I have learned to be comfortable with a certain amount of “close enough”
Interesting that the gauge pointer moves really slow. On my '83, the pointer jumps right up. Maybe some type of voltage stabilizer, a la MGB ?
Now to swap out >>
FOLLOW up on swap out – old unit had plastic float filled with fuel.
The float had some rubber rings around it for bumping against the tank maybe - they were ready to fall apart. Suggest getting a piece of appropriate foam from a junked car to keep on hand.
Reading on OEM sender:
238 ohms empty
18 ohms at Full end of travel
**
‘Slow’ is normal, Louie - it’s the characteristics of the gauge…
Frank
xj6 85 Sov Europe (UK/NZ)
**
I’ve spent ages calibrating the fuel senders… Not easy, especially to make both read exactly the same.
The bronze axle that the arm is mounted has a slot in one side. With a screwdriver you can adjust the arm’s relative position of the rheostat If the gauge does not go to Full when the arm is at it’s top position.
It needs to be moved in very small increments. Minor adjustments can be made by bending the arm.
Put the new sender in the car and fill up the tank to the brim.
Mark the position of the fuel gauge.
When tank is at 1/3 remove the sender and find in what position the arm gives you the same reading at the gauge. Now you know what the position of the arm is when the tank is full.
Adjust so it reads full. Make sure though that it also reads Empty.
The rubber rings in my senders where also falling apart, I removed them with out any ill effects.
I went through this 20 years ago with my 1987 XJ6. Float developed slow leak in it, took on fuel, gave low reading. Swapped out float, problem ‘mostly’ solved, as when I fill the tank as far as it can go without spilling fuel beyond the filler cap, guage still sits just slightly below the ‘full’ mark. On my '86 car, one year older, never encountered the problem. Go figure.