2009 Nissan Altima 2.5 s has 100,000 mi exactly fuel gauge would stay stuck on empty and sometimes on full put a brand new fuel pump in gauge worked fine for a couple days then went right back to getting stuck on full then empty then sometimes working any ideas
It's unlikely that your old fuel level sender and your new fuel level sender are both bad.
If you still have that old fuel pump maybe test it.
Here's what the resistance values should be between Fuel Pump Terminals 2 and 5 at FULL and at EMPTY
If you know how much gas is in your Altima, you can also test the connector on the new fuel pump without removing it to see if the Ohm reading seems reasonable.
That will conclusively determine if this is a problem with the variable resistor for the fuel gauge on the fuel pump module or if it's something else.
Frankly from what you described this seems more like a wiring issue.
Why did the issue temporarily fix itself when you replaced the fuel pump?
I think it's because you "jostled" the fuel pump wiring harness or perhaps when you unplugged/plugged the fuel pump connector.
I took a screenshot of your fuel pump harness and a couple of things seemed like possible explanations for what's happening here.
Here' the screenshot:
So the problem could be a loose wire in the fuel pump (harness side) connector so check that connector first. Give those wires that go to terminals 2 & 5 a little tug from the backside to make sure they're connected good. Look for any signs of corrosion too.
The other thing is that when you pulled the backseat out it's likely that that wiring harness was slightly jostled by the bottom of the seat.
Maybe inspect that wiring paying close attention to the wire colors that go to terminals 2 & 5 on the fuel pump module (fuel gauge).
Lastly, look at where the fuel pump wiring enters the large harness that goes under the trim and then under the back door.
Wiring under a door is always a place to suspect when looking for a break in the wiring because water causes corrosion and a failed door gasket can allow water to soak the harness.
Check the pins in the connector on the vehicle harness connector for the sending unit and make sure there is no corrosion and the pin fits are tight when connected . Sometimes if it’s pin fit you can wiggle the connector and get the gauge to react
The fuel sending unit is faulty. Replace it.
The brand new fuel pump I installed was an all-in-one thing came with brand new sending unit and everything all I had to do was take off the old one put the whole new one in with all brand new parts but a week later the fuel gauge started acting up again
The part you used might be faulty. Was it OEM or aftermarket?
Bought it from 1A Auto I believe the brand was trq
If I were you, I would return it and get the OEM part.
Ok thanks for the help
You're welcome and good luck.