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Fuel guage reading backwards

Before installing this pump/sending unit my mechanic confirmed that my '88 4.0L unit had the same part number as the '91 2.5L pump I wanted to swap in. How can this be?

There's gotta be an easier fix.
 
Chrysler reversed the polarity of the gauge sending units in 1991. The fuel pump may have the same part number, but the fuel level sender does not.

Just reverse the wires. Except there are only three wires ... one feeds the fuel pump (that's the fat wire), one feeds the sending unit, and the black is ground for both the pump and the sender. Best way to do it is to pull the fuel pump out of the tank and reverse where the wires connect to the sender.

The gauge will be slightly inaccurate because the old sender had a range of 0-88 ohms and the new one has a range of 105-5 ohms ... but the fuel gauge isn't exactly 100% accurate anyway, so you'll probably never notice.
 
Eagle said:
Just reverse the wires. Except there are only three wires ... one feeds the fuel pump (that's the fat wire), one feeds the sending unit, and the black is ground for both the pump and the sender. Best way to do it is to pull the fuel pump out of the tank and reverse where the wires connect to the sender.
Only one wire connects to the sender, as the ground goes to the pump chassis. Where do I reverse the wires?
 
I can't help myself. I gots to do it. Don't ask me why.
Fuel gauges are just like wifes there never right. Most of the time just ignore them. But do remember to put a little something in them from time to time so they don't up and leave you stranded.
 
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