Please excuse me if I come off as an idiot, I don't know a lot about cars.

I do know my gas gauge has been extremely off ever since I got my 2002 SS Monte Carlo (over a year ago). It fluctuates a lot, and today I was completely on empty with my low fuel light on, filled my car up and it only took 13.5 gallons. I know the tank is 17 gallons, so obviously something is not right. My dad just recently replaced the fuel pump (and if I'm correct the float which controls the gauge is in that) and it didn't fix anything. What's wrong and what can I do?

 

Hello Cassie,
You are right. The sending unit is in or connected to the Fuel Pump. If you are still having problems ir may be that the Gage itself is bad.
Does the Gage fluctuate when you have the car running But you are sitting still? (when you start it in the morning or after work/school)
Most gages fluctuate, But normally not when the car is sitting still and the fuel in the tank isn't sloshing around. So if your Gage is moving when the car had been still for about 5 min. the Gage may be bad.
Keep on checking this post. Other members may have other ideas to help you. Good Luck. Welcome to MCF and Safe Driving!

 

It does not fluctuate when I'm sitting still. Another example is the other day I was also completely on empty and my dad put exactly 5 gallons of gas to see where the gauge went. It went right between 1/4 and 1/2 of a tank, and he said that was right. Then once I started driving it went up to over 1/2 a tank. Also whenever my car is on full, it stays there for what seems forever (one time we even thought it was stuck because it stayed there so long) and then it drops very quickly once it moves from Full.

 

iI's almost nothing and something you get used to. Mine has been that way since I bought it. It stays on full for a bout 60-70 miles and then drops. When mine hits empty, I still have 6 gallons (it's an 18 gallon tank.) Once you figure out your MPG, you can figure out when you're actually empty.

 

Is there no fix for it? It's so annoying and it makes me nervous.

 

When I fill my tank it does the same thing. Stays at full for 70 to 80 miles. Then it start to move. Fast for the first 8th of a tank, then it moves as I would expect for a Chevy/GM gas gage. I've owned many cars,pay GM products. I've found in my yrs that Analog gas gages just aren't accurate.
There is a saving grace of the 00 - 05 Monte is the Digital Info center over your rear view Mirror. It tells you your gas mileage, fuel used, range with fuel left and current miles per gallon. And the Range indicator is a good substitute for the gas gage. I mean, you don't want to make a 50 mile trip when it says your range is 25 miles.

 

My dad has owned many GM cars (he works there) and they've never had this problem before. Also my info center is useless when my low fuel light comes on, for my range it just says Low (even though I apparently have at least 3.5 gallons left).

 

It maybe your stepper motor in gauge bad. I had the stepper motor go bad
on my speedo. GM had a bad batch on stepper motors..

 

True the Range setting says low when the low fuel light come on. But before that, it will give you an almost perfect indication of how far you can drive Before you have to fuel up.
Last night, I had 72 miles to drive to get home. My gauge said I had just over a quarter tank. I checked the range and it said I had 97 miles left. Gas is cheaper in my neighborhood then where I was. Needless to say, I made it to my home town and got gas. The Range indicator can by reliable if you test it out a few times to feel in your mind how accurate it is

 

Cassie Marie:

JC has given you some great info as far as calculations VS what the gauge is telling you....

Im curious, How many miles are on your Monte?...

As jerry Mentioned.. It could possibly be a "stepper" motor...
I would even suspect a fuel pump/float issue depending on the Miles on your vehicle?

Im guessing you bought it 2nd hand? Another issue that will tend me to believe it could possibly be a fuel pump/float issue is:
With gas prices being what they are... That im sure people who owned before you may have ran it right down to empty...Which causes it to start to pump/pickup/ reisdue in the tank...(Dirt/rust etc) that settles in the bottom of the tank over time.... Thus causeing a similar issue....

I can fill mine up as mentioned by JC and the gauge wont move until I also have traveled over 70 + miles.... It does vary a little under acceleration and or brakeing.... But not an awful lot...

I hope this helps!
Maybe someone else will be able to recommend other ideas as to narrow down the probable fix!