I just bought a 1988 F350 4X4 with dual tanks. When the switch is set to utilize the front tank, the gas gauge doesn't seem to be giving an accurate reading. It seems to be ok to a point when full but once a certain amount of gas has been used, it becomes unreliable. I'm thinking it might be the sending unit in the tank. If it is the sending unit, can I fix it or do I have to buy a new one? I'm a fairly good mechanic at 63 but have never done sending units. How often is it the gauge the culprit? The rear tank readings are good which leads me to believe it's the sending unit. Haven't looked yet, is there a drain plug in the tanks? If the sending unit can be fixed, what's the procedure?

Thanks

Rick
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Rick, if one of your tanks reads about right you can indeed rule out the gauge and instead suspect the sending unit of the offending tank. I don't know if they can be repaired, I know floats can be replaced if they get full of fuel and make the gauge read empty all the time, but I think the sending unit itself is a non-serviceable item...

 

The sending units in these trucks are pretty straight forward. The arm moves along an electrical contact strip (I'm definately not describing this properly). On my truck, a portion of the front tanks contact strip was gummed up. When I changed pumps I cleaned up the contact area of the sending unit. If you remove your pump and sending unit assembly you'll see what I'm talking about. It was pretty straight forward and I'm not too bright.

I should preface that my experience is with a 94. I'm assuming that the basics of the sending units are the same.