...and taken apart. Float seemed to run up and down ok but cleaned everything anyway. Two silver wires and one copper wire all look ok. Is there anything else I should look at before putting it back together?

No, that should be it. You could have simply taken a tall glass and filled it with lacquer thinner and set the assembly in it. Pin hole would fill up the fuel cylinder. Slosh it around after setting for awhile with your finger over the hole.. Repeat several times. Drain out thinner. Tilt cylinder back and forth and listen for float moving. Works 99% of the time.

After putting the sender back together and installed, gauge correctly shows near empty with warning light on - after putting 13.8 gallons in the tank, gauge shows only 3/8 full.

I had this problem before. After chasing my tail around a few times, I discovered my gauge was bad

The resistance of my sender was 67 ohms empty, and 9 ohms full. If those readings are close on your sender, look at circuit resistance and the gauge. A jumper wire across the sender should drive the gauge to "full".

Measure the resistance across the sender when the tank is empty and when it is full. A full tank should give you very little resistance (I think something like 10 ohms) and an empty tank more like 80 ohms. If you don't mind making a mess, you can take the sender out of the car and measure when it's right side up and then when it's upside down (allowing the float to slide to what would normally be the top) instead of filling and draining your tank multiple times.

--DD

I'm reading 40 ohms with a full tank

I checked the Factory Service Manual in Section 2 Fuel system and Section 9 Electrical and there are no values given. I think a full tank should be around 10 ohms. I want to say the scale is 10-90 ohms but not finding any validation.

I just had my tank out. From bone dry I measured the sender resistance. I added 1 gallon at a time and recorded the values at every single gallon. I charted a beautiful curve right up to 15 gallons.

His 40 ohm value suggests about 1/2 a tank. I'd say the sender needs some scrutiny.

I'm sure every car has slightly different values. I would love to see what other people measure. My motivation was finding the exact amount of fuel left when the red light comes on. I believe it was 3 gallons.


When I mentioned the jumper, I meant jump the wire harness pins to fool the gauge in thinking the tank is full. (Low resistance.)

I replaced the fuel sender this morning and now the gauge is reading full as it should since I just filled the tank. Will see what happens as I burn fuel this coming weekend.

If i'm not mistaken, it should be 5 Liter ...

'74 owners manual states 1.6 US gallons/6 liters

In my excitement to write down the resistance values, I may not have caught the exact moment the light went out.

Sounds lame, but I know it was UNDER 3 gallons.


Anyway, I'm glad you got it fixed!