2001 Express Van 3500, Fuel Gauge Problem

-- In-Re: 2001 Chevy, Express 3500, Cutaway Van, 5.7L V8 Gas, RPO# CG31503 -- Fuel gauge was working fine. We purchased a NAPA replacement fuel pump with fuel sensor. After installation, then the gauge just reads empty. When key is turned on then gauge goes up slightly from empty and fades back to empty. We checked the sending unit. When moving arm it reads from about 40 - 250 ohms. At sensor the Ground wire has continuity to ground. At sensor Gauge wire reads 0 volts with key off and about 6 volts with key on. All connections look clean and solid, including the one at the cross member -- Any ideas why after changing the fuel pump, then the gas gauge now stays on Empty ???