I would agree with John that you use (replace the Mitsu unit with) a correct sending unit for your guage. It might require a trip to the local radiator shop to solder the old hole shut and put in a new mounting flange.
If you feel the need to check the Mitsu sender, one of the wires is for a controlled-voltage input and the other is a ground lead to the body. Remove the sender and look at it, you should be able to tell which is which. Then hook a multimeter to the wires and move the lever up and down. The resistance should change in a linear fashion from about 1 or 2 ohms to perhaps 90 ohms.
One of the issues you may find with using the original guage with this sender is the resistance direction. That is, whether it has high or low resistance empty and the reverse when full. Most of the older Chevys were opposite of what is used after about 1970, regardless of car brand. So even if the sender works, you may get an empty reading when the tank is full and vice-versa. That works, but it's kinda ghetto.
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David
newbie #4153
