the gauge works but when I fill it up it reads 3/4, i'm not sure where empty is and don't really want to find out, is there a calibration method or is it a replace?
thanks
mike

 

I would start by removing the sending unit and inspecting the condition of the float and arm. If the gauge is moving, the issue would seem to be at the other end of the system.

 

If I am not installing a new sender with adjustment instructions this is what I do. With the sender removed from the tank measure the distance from the mounting flange to the bottom of the tank, lets say it is 20". Now go to your sender, if it is the type where the resistor with the arm attached is adjustable it should be 10" down from the mounting plate to the center of the arm pivot hole. The arm will be 10 to 11" long, when lifted up it should be just below the mounting plate. when hanging down it should measure 19.5" from the mounting plate to the bottom of the float ( I deduct the half inch from the total so the gauge reads empty when there is 1/2" fuel left.

Once you have confirmed your measurements take the sender to your truck and connect the sender and ground wires without installing the sender. If your sender does not have a ground wire run one temporarily from the sender to the tank. Turn your ignition key to the run position (not start) and slowly move the sender arm from one extreme to the other. It should read empty all the way down, full all the way up and aprox 1/2 in the middle, if it does you are good. If it does not read full and empty when you do this test you have a mismatch between the gauge and sender, one will need to be replaced. If the gauge moves smoothly as you move the arm then suddenly jumps to full or empty you have a bad sender. if you get no movement at all you have a bad ground, sender , gauge or wiring.

I have been testing senders this way for 40 years, works on almost everything made.

 

Has your truck been converted to 12v? If so, what are you using for a voltage drop to the gauges? Mine reads closer to 3/4 when nearly full no matter what (12v conversion). I don't like to fill into the filler neck, to avoid sloshing out.

You can test the gauge head (in dash) by connecting a 1.5v D-cell battery across the terminals (with wires disconnected). It should read 1/2 full. (give it time to settle)

 

I built a cardboard box with the inside dimensions of my gas tank to check the sending unit movements.
TractormanBill

 

Very good idea. Thanks.

 

it has been converted but I'm not sure what being used if anything, although
all the gauges look period correct they all look new. i'll be digging into it shortly as I redo my interior this winter.


tractormanbill, great mockup


thanks for all the great ideas guys.


mike

 

I always adjust mine by filling the tank to half full (8 gallons if you have a stock 48-52 tank) and then set the float level so that the gauge reads half full. Just make sure the float is free to travel and doesn't hit anything. The rest takes care of itself...