Is there one? If not how the the fuel gauge get its reading? If it does, where can I get one? My gauge always reads full when I turn the key on.

 

There is one. Quite often the float gets stuck though. Have you filled your tank ALL the way up and let it stay like that for a while? That'll usually get them moving.

Failing that, there may be some kind of connection that has failed somewhere.

Good luck

 

The electrical connection for the sending unit in the gas tank are near the drivers side rear wheel, up by the fuel fill tube. This is where I'd start.

 

Cool! yep I knew it, I am going to have to remove it. Do you know where I can get one? Schucks does not list them.

 

I bought mine from mazdatrix

 

Badass hulk, thanks.

 

A lot of times you can simply remove it and clean it up a bit to correct these issues...

 

On my 1979 the gauge will never read more than 3/4 full even with the tenk absolutely "topped off". Is this likely to be a wireing/connection issue or a take the sender out and tweak it issue? some other fix?
Sorry for the hijack, but our problems sound similar, so I thought any fixes that turn up might be best if attached to your thread.

 

anyone know what the readings are for full/empty? The range I guess electrically?

 

the sending unit has contacts in which a rod attached to the float rubs against. If it should become corroded or the rod worn, it won't send a signal to the gauge. If the 2 prong connector should get corroded you will get an intermittent reading or no reading at all. I am going to pull the sending unit and clean the contacts and put it back in.

 

Good info, let us know how the procedure goes. Any chance you could snap some pics while you're at it? My gauge is also a little less than accurate, so I might be following in your footsteps soon...

 

The fuel sender changes the ohms of the signal sent to the gauge. How does one change an ohm reading, you change the resistance on the wire. In the sender, this is done by lengthening/shorteing the wire that the signal passes through. There is a bar inside the sender that has a wire wrapped around it. As the float arm moves up and down, a contact tab moves across the bar and the signal goes through more or less of this wrapped wire.

The problem with this setup, over time, is the contact tab wears through the wire and it breaks. Often results in a partial or non signal, depending on where the break is. There is no repair for this, only replacement.

Ohm readings per the 83 FSM are 95 Empty and 7 Full

 

I just had to replace mine. The connections where so corrodid that they just broke off. We awaire of the sticker price since its $111 to replace.

 

Great info! The gauge reading low could easily be caused by added resistance due to corrosion. I will clean them up and see what happens.