Fuel Tank Sender

My fuel gauge reads empty when the tank is 1/3 full, which is about 9 gallons of fuel.. I took the sender out of the tank to test it. The range and length of the arm correspond to the level in the tank. The float is about 1-2 inches from the bottom of the tank when the gauge reads empty. The float is near the top of the tank and the arm is horizontal when the gauge reads full. When I reinstalled the sender in the tank, it read 1/4 full when the tank was a little over 1/2 full. Any ideas how this could be? I don't suppose the float could have lost buoyancy.

Gary S wrote: If you decide to change these are the way to go.

+1

Jim,
If you do get a VOM and test the sender, the Ohm reading will be linear from about 33 to 240 with the 33 will be the empty reading.

KENO wrote: 8122pbrainard wrote: Jim, If you do get a VOM and test the sender, the Ohm reading will be linear from about 33 to 240 with the 33 will be the empty reading. Pete I don't know what he has for a gauge setup but your numbers are backwards for a 33 to 240 ohm gauge. 33 ohms would be full and 240 ohms would be empty on American applications, it's an industry standard If you ground the sending unit with the key on, the gauge should go to full.

Ken,
Yup, you are correct. I'm backwards this morning! In any case, as mentioned, getting the VOM out to testes the sender only.

I hear what you are saying regarding VOM testing the sender. However, the sender operated properly when it was outside the tank. Doesn't that confirm what VOM testing would confirm? What would cause the difference is performance of the sender inside vs outside the tank other than the float?

Swing arm floats in a boat vary quite a bit. The reed switch WEMAs are the way to go. Since it is out (which can be a pain to do), replace it with a less variable, bullet-proof one. All done and it will measure as you expect. They swing arm styles have way too much potential for fussiness.

KENO wrote: Here's a thread from last year about the reed switch senders. I have one that's decently accurate like Air206's., Looks like JQ's wasn't so accurate. thread

The accuracy of mine is not the sender, but rather the fact that the specific unit I got should really be 1 inch longer. Then, the accuracy would be fine. It reads about 1/4 "off" because of the 1 inch too short issue.

JQ