Hey guys, I just got a 93 Firebird Formula, good condition for the most part with 80k on her. The gas gauge doesn't work. After fill up, it will go to F, then keep track till you hit about 3/4th's tank. Is this a problem I need a new sending unit for? Are they hard to change, do I need to drop the tank? Thanks in advance guys!

 

the tank is shaped like an upside down cam lobe...the top is wider and takes longer to deplete. once you get below about 1/3 it really starts eating away at the guage. if you're really concerned about it, check the mileage it takes to get from completely full to about 1/2 then check how many miles it takes to get from 1.2 to 1/4. fill it back up to 1/2 (paying attention to how many gallons you put in) then fill the rest of the way. the mileage should be the same...around 23 for a stock motor. i was getting about 25 when i was stock and now i'm getting about 23 with my 383

 

Before I'd drop the tank, try a can of drygas in the tank a couple of times and see if it clears up. Strange as it sounds, something in it cleans the sender unit.
Doug

 

I don't even use the fuel gauge. I reset the trip meter every fillup. When it hits 200, I fill it up.

 

I fill up when the light comes on...

 

Don't drop the tank, it's not worth it. Look up the access hatch on here if you decide to do anything to the tank. I've dropped the tank and cut the hole with my buddy on his Trans Am and the hole is a whole lot easier.

 

Is the low fuel light seperate from the sending unit, so even with a bad sending unit it will light up when I'm actually low on gas?

 

woa...you have a light??? either i've never let it get that low or i dont have one.

i usually fill up at the 1/4 too...but a few times i let it get waaay down there, uncomfortably so.

 

It's the "Check Gauges" light.

My tank has about four gallons left in it when the light comes on, but the needle is one needle-width above the empty slash.

Actual empty must be way below the E, because I let it get down there the other day and there were still two gallons in the tank.

 

Do you realize the fuel acts as coolant for the pump?

If you ever run out of gas, you will overheat the pump and it will have to be replaced. It ain't cheap, either.

 

Yes, I know how fuel pumps work.

As I said, there were two gallons left in the tank. I don't plan on letting it get much lower than that.

 

I had a pump fail on me on the road. It was towed to a garage instead of my home. I paid $550 to have it installed and ended up with a change in my gas gauge calibration. I found out the hard way that the car runs out of gas before the gauge shows 1/8 of a tank. New pump and I already stressed it. I can smell gas now when the tank is near full. I suspect the filler neck got cracked during the tank removal as the splash cup ended up getting broken. One of these days I will pull the tank down myself and see about straightening out these foobars. My life is too full of these borked garage repair stories.

 

When I fill my car up it goes way past the F. One day I ran it low to right about the E. I filled my car up at a station and it held almost 15 gallons of fuel. I now know when my needle is approaching the E my car is burning vapors.

 

Fill your car up at the "half tank" mark and you'll never have to worry. I've only let it go below the quarter mark a handful of times in my 3+ years of ownership.