I would definitely start with the wire connection under the battery. You Texas guys are lucky, it takes a lot longer for the corrosion to set in then it does up here in road salt land.

The connection is pretty lame from Dodge. There are 3 or 4 small wires that enter one side of the connector, and 3 or 4 small diameter wires that come out of the connector. Then they wrap it with tape and put it under the battery where the corrosion is probably the worst. Those wires at that one splice are the 12 volt feed to nearly everything that gets battery power. If you have more then 5 volts, but less the 12 volts, that connection is probably bad.

For the test, at that one connection you had 8 volts, you can provide 12 volts to what that terminal connects to and see if the pump runs. If the pump runs, the wire connection is corroded. Anything 5 volts or less is powered by the computer, you DO NOT want to supply those connections with 12 volts.

For the record, that wire nut patch on the 93 Dakota 4x4 wiring outlasted the truck frame by more then a year. Gene