Well my fuel gauge didn't work after I put the new gas tank in, and i found out it was because the old wire wouldn't mount up to the new stud on the tank. So, I did a little rewiring, and it is on there very well now. Problem is, it's only reading just above halfway full (and the tank is full). At one time, a few weeks ago, it read full for about 10 minutes, then dropped back down to half.

Any suggestions? I know the wiring at the tank is good, I'm thinking maybe the gauge?

 

More likely the float in the tank is either hung up or installed upside down

 

well dang ... i guess that could be it. How is it supposed to look installed?

 

or the float's got a hole and partially flooded.

The only choices you have are to remove and fix the float, or live with it.

 

To check the gauge, remove the wire at the tank and the gauge should read all the way in one direction. then put the wire to ground and it should read all the way in the opposite direction. any thing else indicates the gauge, wiring or gauge voltage regulator.

 

My gauge has never read full and I have a new sending unit in the tank. It has always read 3/4 full when the tank is full. This is a very common problem with these old Mustangs. When I get to empty I fill up, so I never run out of gas.

 

I would, but I don't know where empty really is! I just usually fill it up once a week or so, and that seems to hold me over, for now.

Genius!!!

 

Mine fills up well past the 'f' and dies at a just under a quarter...

 

Well, you know you have a 16 gallon tank, and the pickup on the sending unit does not sit on the bottom of the tank, so your useable gallons is more like 15. So, the next time you hit empty on the gauge, see how many gallons it takes to fill it back up, then you will know how much gas you had left in the tank when the gauge said empty. My fillup from empty is always less than 10 gallons, so I know that at empty on the gauge, I still have about 5 gallons left in the tank.

 

There is an outside chance that in the course of rewiring the sender, that the connection between the stud/screwand the wire may be less than ideal. If this is the case, then there may be just enough extra resistance to throw the gage off kilter. These gages use very small amounts of current, any disruption may cause false readings.