gas tank mistery: 3 gallon missing

Hi, 1997 Civic LX, 5 speed, US model.

The owner's manual says my gas tank has 11.9 US Gal. Each time the
needle reached the EMPTY line, I refilled and usually I put 8.5-9
gallons of gas. This time I wanted to try higher octane (to
troubleshoot a pinging problem) and I decided to run just a little bit
longer before I refill. Usually a gas tank lasts 230 miles, this time I
run 260 miles and I was about to stop to the first gas station, when I
run out of gas on the highway. The momentum kept me going, I was able
to take the first exit and there was a gas station, I bought a plastic
gas can and went back to my car, then I drove to the gas station and
filled up. The total amount of gas it took was 9 gallons, 1 in the
plastic can and 8 more when I drove to the pump.

So, from dry empty to full I put 9 gallons. The manual says I have a
gas tank of 11.9 gallons. Almost 3 gallons of gas are unaccounted for.
WHAT IS GOING ON???

Now I realize how close I came to running our of gas, almost each time,
thinking I have so much gas left in the tank. WRONG. Then, I felt like
a moron, running out of gas, pregnant wife waiting in the car, hot and
humid outside, you figure it out... not fun at all. she wants a divorce
now!!!

To add insult to injury, my experiment also failed: the sound that I
thought was pinging is still there, even though I filled up with 93
octane (usually I get 87). True, I drove only 15 miles since the fill
up, maybe it needs some time to clean the pipes and the fuel injector
of the old gas, or perhaps the engine needs a few more miles to adjust
to the new octane, but still, if the sound remains, I wonder what it
is. If it does not go away with 93 octane, then it is not pinging...

weird. I think this car is haunted. and whatever it is, it lives in the
gas tank, it takes up a volume equal to 3 US gallons, and it makes a
sound similar to pinging. Anyone want to buy this car???

 

Oh, one more thing: the low fuel light never came on!!!

 

Did you find out whether or not you have a Knock Sensor on your car? If
not, you need to check the timing. I once owned a car that did not have a
knock sensor and found out if I slighly retarded the timing, that it
solved the pinging problem. I should note that if you retard the timing
too much--your engine will run poorly.

 

not yet, I am going to look in the Haynes manual right now! But will a
defective know sensor cause pinging with 93 octane???

 

no knock sensor, Will retard the timing tomorow. Thanks!

 

Your car has to be empty on the side of the road to put in 11.9 US Gal.

 

I run out of gas. Isn't that "empty" enough? yes, it was on the side of
the road... and teh pump shot of at 9 gallons, not 10, not 11, not 12.
that leaves 3 gallons unacounted for. Unless there is water or
something else in the tank.

thanks

 

I agree that this is a problem. While there is such a thing as
unusable gas in the tank, it should not be anywhere near 3 gallons in
a 12 gallon tank. Have you inspected the tank for obvious physical
damage?

 

Where was the gage's needle after filling? Some pumps like to turn off
way too early, leading to a short fill. Still, three gallons is a lot to
be missing!

 

the needle was all the way up, actually a hair ABOVE the full line,
like usual. I fill at different gas stations, so this is not an issue.
what scares me is that I came close to running dry so many times, and
the light never came on, and I though I had 3 gallons left in the tank
I had not!

 

Are you sure you even have a low fuel light? My '94 civic does not.

 

Just such a condition came up here a couple of months ago. Fellow found
a huge dent in his tank, as I recall. Check the tank, chitbul.

 

Whoops, make that chibitul. Sorry!