So I have a 1989 F250HD with dual tanks. Since I bought the truck, the fuel gauge has worked, but in a very screwy way. When the tank is filled, the gauge will read far right off the full mark, and just stay there until there is about 6-7 gallons left in the tank, at which point it goes to about the halfway point and jumps around pretty crazily for a while. It continues to jump around the halfway point until it gets to about 2-3 gallons, then it drops straight to empty. It does this quite reliably, so I don't really fear running out of gas, it just would be nice for it actually to work right.

Symptoms are exactly the same for both the front and rear tank. What should I test first? The switch? The gauge? And how do I go about doing that? I would think the sending units are okay since the problem is the same for both tanks. Thanks in advance for any suggestions.

 

Can anyone help?

 

Deleted, deleted.

 

Is that a voltage regulator for just the fuel gauge or is it for the whole dash? My other gauges work fine.

 

my 88 does it as well, i remember reading a while back that it is the sending unit in the tank, and that its premature wear from being shipped or something. anyway, that post said that the only way to fix it is to replace the sending unit, without a fuel pump they run around 80-90 bucks, with a new fuel pump they are around 110-120. wich is probably what i will do since my pickup just lost the front lift pump.

 

I take back what I said above. It looks like you do not have a voltage regulator in 1989.