Basically my gas meter will say I have plenty of fuel for long periods of time, but then plummet down as much as a quarter. And when I'm driving, the meter will either go up or down, and then change back at idle. I'm filling up sooner and sooner than I need to every time I go to the pump. So it's definitely getting worse... has anyone had this problem?

 

extremely common problem with LT1's and just Fbodies in general.

the rule of thumb is:

when the gauge reads over full, you are actually just full,

when the tank reads just at full you are really at 3/4,

when it reads 1/2 you are more near a 1/4 really and,

when its 1/4 of lower its almost empty.

just try and always keep it above a half a tank if you are worried, that way you wont burn your pump up as easily.

also the gauge will go up and down while accelerating because the float moves as you accelerate causing it to get a false reading thinking more fuel is in the tank than actually is and vice versa when you brake.

 

My cousins 93 ta is empty when the tank shows 1/8 of a tank left.. My 95z doesn't have much of a problem for the time being. Just reset your trip whenever you fill up, unless you don't have a "normal" driving area (city/highway) then this probably won't help as much.. But if you only drive city and or few highway miles, vise versa and know how many miles you can run to a full tank, then set the trip and just drive without even looking at the guage.

 

Oh yeah and when it hits E its def. empty. I ran out of gas once many years back. In my third gens you could probably go a good 15 minutes with the needle sitting on E, not the case with the 4th gens. I was slightly above the E and had a 10 mile trip back to base. Sure I'll make it I thought, I stalled out and ended up walking to the base at 3 AM in the chilly fog. Yeah fun times!

If the gauge is nearing 1/4 mark I make sure and find gas ASAP.

 

The problem is the shape of the gas tank. I just reset my trip meter and fill up when ever it hits 200 miles no matter how I drive it. Usually it takes about 10-11 gallons.

 

Yeah, the gas gauges on these cars definitely suck. 1/4 tank = get gas, lol.

 

I'd really like to get an accurate reading... what are my options?

 

When I first bought my car I had no idea of this common problem. 1/4 tank my car dies, I push it to the gas station (died right next to one) fill up and no start. Blew the fuel pump, put a new one in and my first full up the gauge goes all the way past F. WTF

Anyone put an LS1 plastic gas tank in and it maybe fix the problem?

 

Just take the advice given above... just think of 1/4 mark on the gauge as the new empty. If you really wanted to, here's a possibilty I have heard talked about but never seen anyone actually do it or say they did it. you could fill up the tank, keep the ignition in the on position and then pull the needle off the gauge and put it back on at the F instead of showing a 1/4 over F. If that were done I would use just under the 1/4 mark on the gauge to signal time to get gas though, but you'd have a little more time before you're on fumes.

But the reason the gauge reads like it does is the profile of the tank as already mentioned. Attached is a pic of the side profile of the LT1 tank. The LS1 tank has the same profile. What you see on the gauge is really showing fuel level in profile, not fuel capacity. when the fuel in the tank is halfway down the tank if you were looking at it in profile, the tank is not holding half the fuel it's capable, since the lower part of the tank does not have the same amount of area/volume as the topside of the tank. the reason the gauge will hover at full for so long is becuase the fuel actually completely covers the fuel level float and basically locks it there until you've drained some fuel off. Even if you moved the needle, the gauge will still stick on full for the first ~1/8-3/16 of a tank or so. Even if the float did go to the top of the tank and truly showed full, the halfway mark on the gauge still wouldn't mean you're carrying half the fuel capacity the tank is capable of. Just remember what you're looking at on the gauge is fuel level, not capacity.

 

That's an extremely stupid design.

 

Welcome to driving an F-Body my friend. My car ran out of gas driving home from buying it

 

Mine is fairly accurate, but I have only been below 1/2 tank on the gauge once. I was in the middle of nowhere at 10 at night. I was driving up to a college I was looking at and I thought, oh, it would be cool if I could make it up there and back on a tank. I left a little town with about 1/4 tank and thought, eh, no biggie. Got 10 miles and the gauge was on E. Thankfully the next town was about 2 miles further. I actually shut the car off coasting into town and pulled in the station. I put 15.4 gallons in the 15.5 gallon tank. I did go 398 miles on 15.4 gallons though. So I did got about 26 on the road. Not too shabby for an A4 LT1. The gas gauge is actually broke in my T/A. I just fill it up every 200 miles.

 

Are you actually filling up sooner each time because you are using more fuel or because you don't want the gauge to go below a certain level? If you are driving the same amount of miles but filling up sooner you are probably burning extra fuel or loosing it.

I have the same problem with my T/A and I have kinda got used to it now after 5 months. Just fill up at a 1/4 tank on the gauge.

 

i fill up at around 200 miles.. usually takes about 12/13 gallons.
im getting about 17.5mpg with city and highway and beating on it.
i ran out once, and it was the last time. lol.

aaron

 

What I mean is the gauge is getting worse, in that it shows I have a lot less than I actually do. For example, I'll fill up 14 gallons one week, then 13.5, then 13...

 

hahaha, that is hilarious.

It is man, i have EXACTLY the same problem. i wouldnt say its a problem, but rather a design flaw. Over full = full. full = 3/4, 1/2 = get gas. LOL. oh well. its okay, as long as you have a general idea... if you're cutting it that close you should get gas anyways. who can complain now? gas is so cheap.

 

Same here.

We called the dealership we bought it from and they brought us gas. We went to start the car, and the battery was dead. The guy tried jumping it - nothing.

He went back to the dealership and brought us a new battery.

I must have ran out of gas in that car 15 times.

 

I've ran it down to Empty twice, I actually ended up having a malfunction with my Sending Unit, I had to get in there and take it apart to fix it. It would drop to 1/4 and stay at that till it ran empty.

 

i normally go 260-270 miles then fill up with 13 gallons everytime. i've gotten used to it just don't take long trips when your sitting close to a 1/4

 

The shape of the tank is not a design flaw. If they kept it symmetrical for perfect volume indication, you would have lost capacity. It's not hard to figure out how it works, even just by looking at the gauge itself if it is not malfunctioning. The only thing that could be considered wrong is the fact that when full it reads quite a bit past the full mark.

If it's soooo difficult though, just watch your mileage. I knew my sending unit was going to **** on the first tank that it happened, because the mileage wasn't matching up with the gauge reading. I kept driving it for a month or two like that, intending to replace the sending unit, but never once ran out of gas. I ended up totalling the car, so I didn't have to replace the sending unit, but that's another story.

To the OP- If how much you fill it up is changing with what the gauge is reading, your sending unit could be going out. Considering that you didn't know anything about the fuel level indication, I'd say watch your mileage, because you may not have a problem at all.