Fuel Gauge

I just put a new tank and sending unit in my 75. With no fuel in the tank and the key on, the gas gauge goes to 1/2 tank. Does the new sending have to be calibrated? If so, how? any info would be great.

 

You will need to bend the float arm. The float shouldn't be any higher than the bottom of the sending unit mounting plate. This is when the float is raised.

 

Maybe I just don't get it but if the the float is hanging all the way down in a empty tank, how will bending the float arm change the gauge reading?

 

Maybe the current aftermarket senders have to be adjusted, but I've never heard of the need for adjustment if it's the right part. The length and angle of the float arm should be right so that the full range of the sender is achieved in the tank.

If you have a DVM, the sender can be checked before you put the tank in. The service manual shows an ohms reading for empty and full (turn the tank upside down to check as if full). There's a '72 manual at http://www.c104.net/manual/ and the readings should be the same for all intermediates.

You can do this with the tank in the car - but you have to fill and run out the tank to get the readings.

hth!

 

Maybe the float hits the bottom before the...Electrical resistor thingie makes the gauge read empty? (Yeh I know what I'm talking about. )

The only starting point I can be sure of is at full.

I took mine out to seal a fuel leak. You should have seen how bent up the rod was on my sending unit. I even had to bend it to clear the side of the tank. I still think my throw on my rod isn't right. At least I can read it now. It gives me a ball park reading.

 

Jeep used a 73 ohm sending unit similar to some Fords. You need to make sure your sending unit and gauge are matched. Mine had an aftermarket gauge that read 3/4 tank when at 1/4 tank and it was the wrong gauge for the sending unit. Hope this helps.

 

The tank and sending unit are both from 4 wd hardware so they should be correct. The gauge is the stock one. I guess I'll pull the tank and do the ohm check. Thanks for the input.

 

Just installed new guages and sending unit. Definitely check the ohms reading b4 you install. I didn't and the sending unit turned out to be bad. Had to empty the tank and pull it again. (Is easier the second time with new bolts ) Apparently the replacement units are not always the best.

 

use a dvom. it should read 73 ohms empty and 10-12 ohms full

 

when you have the sender out use a dvom to check resistance.empty (float arm down)should read around 73 ohms.full it should read 10-12 ohms