1998 Suburban Fuel Pump wiring harness replacement. On the vehicle are 4 wires in the harness, Black/Gray/Purple/heavier Gauge Black. A mechanic in the past spliced a replacement harness as - heavier Black to Black / Gray to Purple / Purple to Gray / Black to Black&White. The new style harness is a Black / Purple /Gray / Oragne&Black How do I wire this thing? I ASSume- (car to harness) Heavier Black to Black Purple to Purple Gray to Gray Black to Black

Here's a wiring guide for the fuel pump on a 2000 Cadillac Deville: 1. Remove the fuel tank and access the fuel pump module. 2. Disconnect the electrical connector from the top of the fuel pump module. 3. Locate the wiring harness that runs from the fuel pump module to the car's electrical system. 4. Cut the wires on the old fuel pump module connector, leaving enough wire to splice the new connector onto. 5. Connect the black wire from the new fuel pump module connector to the black wire in the car's wiring harness. 6. Connect the purple wire from the new fuel pump module connector to the purple wire in the car's wiring harness. 7. Connect the gray wire from the new fuel pump module connector to the gray wire in the car's wiring harness. 8. Connect the black/white wire from the new fuel pump module connector to the black/white wire in the car's wiring harness. 9. Connect the new fuel pump module electrical connector to the car's wiring harness connector. 10. Reinstall the fuel tank. Note that it is important to follow the wiring guide carefully to ensure proper installation and avoid damaging the fuel pump or electrical system. If you are unsure about any step of the process, it is recommended to seek assistance from a professional mechanic or refer to the vehicle's service manual.

Make sure the ground is good, that truck was known for a bad connector near the Trannie cross member. Find your plug at fuel pump,4 wires..2 black, gray and purple. Black and purple are for the float. Gray is power to pump, black with yellow is ground for pump. When key is turned grey wire gets power check good ground . If power and grounds are good replace pump if not fix ground or replace relay

The gray wire goes from the pump relay to the pump. The black white wire is the ground for the pump. The purple is for the gauge on the dash and the black is ground for the sending unit. I don't list a white wire being used.
If the colors on the truck don't match the tank, you'll have to test them to verify each circuit.

It was an upgrade you need to cut wiring harness and replace it with the new connection system .or it could be a problem with the fuel pressure sensor that plugs into the top of the pump wiggle the wires

I may not be of much help.
According to autozone online, 96-98 model trucks should have - -
gray from relay to the pump
black / white ground for pump
pink - black for gauge ground
pink to gas gauge
You should be able to jumper the pump relay and look for a hot for the pump. You should have two grounds, I doubt it makes much difference which you use for the pump. And then you should have a hot for the gauge with the key on and the relay disconnected.

It should be four wires. Gray is power to the pump, Purple is gauge control, and two black wires that are ground. You should have battery voltage on the gray for 3 sec. after the key is turned on. Did you replace the plug-in to the pump when you replaced the pump? The pumps usually come with new plugs

i know what you are talking about, last time i looked at the wires on the pigtail i cut off and i determined which color went to each pin location. then transfered my findings to the new pigtail.

Assuming you mean replacing the fuel PUMP, the 2 wires are different guages. Connect the lighter wire to the lighter wire and the heavier wire to the heavier wire. If the new harness uses both the same size wires, the heavier wire on the vehicle side (solid black) is for the fuel pump ground. Lighter wire is for fuel guage sending unit.

Purple is your sending unit which is the fuel gauge,Gray is your fuel pump hot wire(positive),Black isyour body ground and white is ground.

I’m happy to assist further over the phone at https://www.6ya.com/expert/joe_a3369546f8067589

GRAY IS FUEL PUMP, PURPLE IS FUEL GAUGE, BLACK IS GROUND,ORANGE WITH BLACK GOES TO COMPUTER.GREY WIRE WITH KEY ON WILL BE BATTERY VOLTS FOR TWO SECONDS UNLESS CRANKING ENGINE OVER.PURPLE WILL REMAIN ON WITH KEY LESS VOLTS THOUGH