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Old 08-14-2017, 07:42 AM   #9
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Join Date: Jan 2005
Location: Kalamazoo, Michigan
Posts: 8,236
Re: Installed '90 GM Factory EFI tank, '72 Blazer Factory gas gauge is pegged past fu

Find the FUEL terminal on the fuse panel, It's on the end in the center. Unplug any wire on it and with the key on run a ground wire from a good ground to the terminal. Your gauge should read EMPTY. If it does then your gauge and dash wiring are good.

Check the continuity looking for Ohms between the ground wires and the fuel tank only, not the frame. You should get a resistance reading on both wires but the purple wire is the one you need 0 to 90 ohms on.

Check between the gray wire and the black/white stripe wire for fuel pump resistance.
The solid black wire may also be a common ground from the truck for both the pump and the sender and it would need to be grounded to the truck at a good ground point before the sender would work. Check for resistance between the solid black and the B/S wire to determine this.

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