Fuel tank level reading issue S4

[gjz30075]

Something's gone arwy with my fuel level readings. In the past, when the level got below 1/4, the needle would be fluttering and the lower it got, the more it fluttered around. All of a sudden, the needle is rock solid now when low. I got suspicous so I filled the tank. The needle rose no more than less than half. Hmmm, so I took an ohm reading at the sending unit and found 28.6 ohms, which is pretty close to 30, which it's supposed to be when full.

I found a Lotus Cortina guage which has part number beginning with 'BF...' so it should respond as my Sprint guage does. However, it, too, only reads less than half; in fact closer to 1/4.

I then siphoned out 2 and a half gallons and took a reading. The sending unit now measures 36 ohms. I think it should read more. I'm assuming I'm close to 7 gallons now, guessing about 3/4 full which should give me close to 150 ohms.
Three questions:

1) Does anyone have any idea how much fuel is in a tank (replacement tank from RD many years ago) when it measures 6 inches on a yardstick stuck down the filler neck?

2) Am I on the right path thinking its the sending unit?

3) voltage stabilizer? I don't know what's in them but the manual says it MUST be vertical when mounted with no more than 10 degrees off center.

Greg Z

[AHM]

for point 2 - I think that if you bypass the sender you should get a full reading

[gjz30075]

You mean by disconnecting both wires at the sender and jumping them together? Or, as I think about this, if I just ground the green/blk wire, it should have the same affect, right?

[sveris]

Your float could be taking on gas, too.

I have only handled 3 Elan sending units myself: 2 of these were the 7 ohms Empty 77 ohms Full type, the other was 0 ohms Full and 90 ohms Empty. One buddy has the 250 ohms Empty and 25 ohms Full resistance range.

Do you know what the Empty and Full readings were for your sending unit before things started to go wrong?

Steve in Ohio

[gjz30075]

Actually, I really don't know the readings when all was working. Just perusing the results of my searching here says I should be at 30 ohms (give or take) when full at 230 when empty.

[SADLOTUS]

Strange this thread should come up right now, my gauge recently, suddenly only went up to half and there was a banging noise coming from the tank.
Thought it might be the float flooded/sunk/punctured and bumping about inside.
Drained the tank and lifted it out, took out the sender.
The arm on the sender was underneath the 'stop pin' so the arm could only go up a little way. It should be between the two stop pins.
Carefully prized it around the stop and reconnected it up out in the open air (as it were), and by lifting the arm I could make the gauge read full or empty as it should.

The float was fine.

What had happened was the baffle had come loose - all those bumpy French, Italian and English country roads? - and had swung back with a wave of fuel and pushed the arm under the stop pin. The banging was the baffle bumping the side. Tank's now off being fixed, when it's back I can adjust the bend in the arm to get the correct full/empty readings.

...well that's the theory anyway.