Gas Gauge Not reading right-goes to empty

My son's 2000 Grand Prix, 3.8L, gas gauge slowly goes to empty activating low fuel light. I changed fuel pump with a boneyard one. Fuel pump works fine but gas gauge always slowly goes to empty even with full tank. Sending unit tested out fine thru range (ohms). Just in case I bought a new sender with the improved copper contacts.

To check, I disconnected the connector at top of fuel pump and rigged a jumper connector using the connector from the old pump. Plugged in the new sender, plugged in harness connector, moved sender arm slowly thru full range. Gauge still goes to empty

Disconnected harness, ran continuity test on pins between fuel pump harness connector and the connector coming thru floor that goes to harness to front Checked out fine. Haven't had a chance to examine harness going to front under carpet yet.

Has anyone had this problem and any ideas where I should start looking? My gut feeling is that there's a loose connector or chafed wire in the body harness going to pcm and dash. Based on my experience thru the years, (approx. 55 years working on cars, etc) the sender should not have to be immersed in fuel to work properly.

Help will be appreciated as it's a pita having to watch the odometer figuring when to fill up; right now that's between 300 and 350 miles to be on safe side. Have gone to 400 miles but that's scary.

i have the same problem with mine.. except mine stays on full till it's empty then the gauge goes rite down from full to empty. i wish i could be of some help but im in the same boat as you.

normally what happen is the teeth of the sender over time get rubbed down and no longer contact the surface of the sending unit to transmit the signal.

Thats what mine did, so i pulled the pump and replaced the sender arm with a new one so that the teeth are touching the sender unit.

Originally Posted by Fivefingerdeathpunch

normally what happen is the teeth of the sender over time get rubbed down and no longer contact the surface of the sending unit to transmit the signal.

Thats what mine did, so i pulled the pump and replaced the sender arm with a new one so that the teeth are touching the sender unit.

might have to try this for mine.

Fivefingers: If you noticed in my first paragraph-last sentence, I have a new sender with the improved solid copper fingers, not the stainless oem crappy fingers.

The sender is not the problem, it's somewhere, something else. I suspect the wiring or a connector further forward in the harness, but as I said, haven't had a chance to get at it yet. I'm also not suspecting the gauge itself, cause if the gauge was the problem, it wouldn't register at all, so that leaves only wiring or connectors.

Bandit, at least I have company with the problem; but I'm sure we are not alone. There has to be somebody around these boards that has deciphered and rectified this type of thing. If only they would share what they've found.